user12898: Among my weaknesses (which I am aware of), the most irritating and the most important for me, at this point, is "checkmate blindness", whether because of time pressure or because of any other reason.
Most of the time I am able to develop a pretty tough attack that forces my opponent to defend and not letting him to seize the initiative.
The problem is that I can't see, too often (!), a forced checkmate sequence and sometimes even mate in 1. Despite the fact that I am familiar with all checkmate patterns and easily checkmating a lonely king with knight+bishop etc.
My question is what is a good way to improve those checkmating skills when the board is not empty and the checkmate is not obvious?
Solving checkmate puzzles doesn't help me too much because I know that the checkmate is unavoidable and I am able to find it. 
For example, this is a game I played yesterday (white). Eventually, I won this game but I did not find the checkmate sequence 5 times!
https://en.lichess.org/B6FRwado

user12901: I'm only rated ~1400 in online chess, but I think I can still provide some advice.
In that game you played I can see three main problems with your checkmating attacks:

You're not exploiting pins on the king. There are multiple occasions where you could have taken the pawn on b6, but you miss the opportunity until later. This is just something you have to get used to. Pins on the king are a relatively simple way of attacking and if you start to think about how you can take pawns, placing the queen accross the king is usually a relatively easy way to grab one, if your opponent is unaware (which is probably the case at your rating).
You close up the position. On move 14, you put your pawn on b5, which immediately loses you a two pawn(!) advantage because it allows your opponent to close the position thereby protecting his king. Admittedly, I don't think I would have found Bc4 in this position either, but even if you can't find it, try to think more about your pawn moves. Pawn moves are especially important because you can't undo them. So instead of playing b5 in that position, you could just play something else entirely.
You let the king run away. Around move 40 you've obviously already won, but something you could improve on is keeping your opponent's king trapped.  Around there you check their king with your bishop, allowing him to run away. If you're unsure what to play, just keeping your rook on a7 is fine. Eventually you can try to move around your rook and bishop to deliver checkmate.

Missing one-move checkmates is pretty normal and pretty much the same as one-move-bunders. You'll improve by playing a lot. One useful thing to think about during the game is to force yourself, every single move, to think about what your opponent's move does: Which square is it undefending? Which squares is it defending?
Similarly, when you're just about to checkmating, try to think about what squares your opponent's king has and how you can take them away during every move.

user12873: It's one thing to be aware of the checkmating patterns, but it's another to have them fully cemented in your mind.  The key here would for you to develop pattern recognition, which happens when you practice these checkmating tactics so much you can almost instantly see them in a real game.
I would suggest just solving countless checkmating tactics day after day.  Do problems that have lots of pieces on the board - the checkmating patterns against a lone King, for example, won't help you much in a complex middlegame.  Probably the best idea would be to buy a tactics book that either focuses on checkmate tactics or at least has an entire chapter dedicated to it.  The other option would be to do online chess tactics, although I don't know of a site that allows you to pick which kind of tactics you want to do.
One chess book you could check out is: "1001 Deadly Checkmates by John Nunn".  It's a fairly well recommended book.

12898: <p>Among my weaknesses (which I am aware of), the most irritating and the most important for me, at this point, is "checkmate blindness", whether because of time pressure or because of any other reason.</p>

<p>Most of the time I am able to develop a pretty tough attack that forces my opponent to defend and not letting him to seize the initiative.</p>

<p>The problem is that I can't see, <strong>too often (!)</strong>, a forced checkmate sequence and sometimes even mate in 1. Despite the fact that I am familiar with all checkmate patterns and easily checkmating a lonely king with knight+bishop etc.</p>

<p>My question is what is a good way to improve those checkmating skills when the board is not empty and the checkmate is not obvious?
Solving checkmate puzzles doesn't help me too much because I know that the checkmate is unavoidable and I am able to find it. </p>

<p>For example, this is a game I played yesterday (white). Eventually, I won this game but I did not find the checkmate sequence 5 times!
<a href="https://en.lichess.org/B6FRwado" rel="noreferrer">https://en.lichess.org/B6FRwado</a></p>
 12901: <p>I'm only rated ~1400 in online chess, but I think I can still provide some advice.
In that game you played I can see three main problems with your checkmating attacks:</p>

<ol>
<li>You're not exploiting pins on the king. There are multiple occasions where you could have taken the pawn on b6, but you miss the opportunity until later. This is just something you have to get used to. Pins on the king are a relatively simple way of attacking and if you start to think about how you can take pawns, placing the queen accross the king is usually a relatively easy way to grab one, if your opponent is unaware (which is probably the case at your rating).</li>
<li>You close up the position. On move 14, you put your pawn on b5, which immediately loses you a two pawn(!) advantage because it allows your opponent to close the position thereby protecting his king. Admittedly, I don't think I would have found Bc4 in this position either, but even if you can't find it, try to think more about your pawn moves. Pawn moves are especially important because you can't undo them. So instead of playing b5 in that position, you could just play something else entirely.</li>
<li>You let the king run away. Around move 40 you've obviously already won, but something you could improve on is keeping your opponent's king trapped.  Around there you check their king with your bishop, allowing him to run away. If you're unsure what to play, just keeping your rook on a7 is fine. Eventually you can try to move around your rook and bishop to deliver checkmate.</li>
</ol>

<p>Missing one-move checkmates is pretty normal and pretty much the same as one-move-bunders. You'll improve by playing a lot. One useful thing to think about during the game is to force yourself, every single move, to think about what your opponent's move does: Which square is it undefending? Which squares is it defending?
Similarly, when you're just about to checkmating, try to think about what squares your opponent's king has and how you can take them away during every move.</p>
 12873: <p>It's one thing to be aware of the checkmating patterns, but it's another to have them fully cemented in your mind.  The key here would for you to develop pattern recognition, which happens when you practice these checkmating tactics so much you can almost instantly see them in a real game.</p>

<p>I would suggest just solving countless checkmating tactics day after day.  Do problems that have lots of pieces on the board - the checkmating patterns against a lone King, for example, won't help you much in a complex middlegame.  Probably the best idea would be to buy a tactics book that either focuses on checkmate tactics or at least has an entire chapter dedicated to it.  The other option would be to do online chess tactics, although I don't know of a site that allows you to pick which kind of tactics you want to do.</p>

<p>One chess book you could check out is: "1001 Deadly Checkmates by John Nunn".  It's a fairly well recommended book.</p>
