user3405: I am a very good attacking and tactical player. There is just one problem. While I catch combinations that might even require 5 or 6 moves, I cannot find 1 turn ones. Let's see this game I played today:
 [FEN ""]

 1. e4 e5 2. Nf3 d6 3. d4 exd4 4. Nxd4 Nf6 5. Nc3 Nbd7 6. Bc4 Ne5 7. Bb3 Be7 8.
Bf4 O-O 9. Qd2 Ng6 10. Bg5 Re8 11. O-O-O c6 12. h4 d5 13. exd5 Nxd5 14. Bxe7
Ndxe7 15. h5 Ne5 16. h6 g6 17. Qf4 Nd5 18. Nxd5 cxd5 19. Nf3 Nxf3 20. Qxf3 Qg5+
21. Kb1 Bg4 22. Qc3 Qe5 23. Qxe5 Rxe5 24. Rxd5 Re2 25. Rhd1 Ree8 26. R1d4 Re1+
27. Rd1 Rxd1+ 28. Rxd1 Bxd1 29. f3 Be2 30. c4 b5 31. cxb5 Bxb5 32. Bd5 Rc8 33.
Be4 f5 34. Bc2 Kf7 35. a4 Rxc2 36. Kxc2 Bxa4+ 37. b3 Bb5 38. g4 f4 39. Kc3 Kf6
40. Kd4 Kg5 41. Ke4 Bc6+ *

I was white. This is the one I am presenting, but there are many games where I missed 1 turn tactics. Please help me.

user2042: The answer is simple and cruel -> evaluation of the position. Unfortunately, being inactive for 10+ years, I suffer from the same problem so I know what I am talking about. 
You will not find a winning move, nor winning lines, unless you evaluate that they are there in the position. That is why you miss those moves -> you didn't even consider that such possibilities exist in the position.
Can you answer me these questions:

How did you evaluate the position in the game, after your opponent played 17...Nd5 ?
Did you even consider 18.Bxd5 cxd5 19.Nxd5! since 19...Qxd5?? 20.Qf6 Nd3+! 21.Rxd3 Qe5 22.Re3! Qxf6 23.Rxe8# mates? Did you see this line, and if you did why did you dismissed it?
Why didn't you play 19.Bxd5! with the same mating tactic as above, instead of weak 19.Nf3 ?

What I am trying to say is that you didn't evaluate the position properly. Maybe you thought it was advantage for White ( +0.80 or something similar... ) while I believe it was won for White ( +1.60 at least ). 
I strongly believe that you would have found these lines on your own if you thought you had a won position. 
Solving tactical puzzles can fix this problem to some extent, but you really need to learn how to evaluate the position properly and this comes with experience. Reading books about typical middlegame positions helps as well, so does strong knowledge of endgames. These will help you in the beginning.
I advise you to start with tactical puzzles, and then move towards typical middlegame positions.

user2001: It is a common problem to calculate all the variations and then suddenly realize that the first move was simply terrible. Actually, there is a rule that should be applied after finishing a complicated calculation, the Blumenfeld rule!
The Blumenfeld rule is formulated roughly as follows. After finishing a complicated calculation, take a fresh look at the position on the board. Try to picture the position directly after the next move you plan to make. Check whether you are missing something trivial. Are you perhaps losing a piece after this move? Are you missing a simple check that makes you lose material? Perhaps you will even be checkmated in a few moves? Only after completing this check for terrible blunders can you now go on and make your move.
This rule does not come easy to any player at any level!

3405: <p>I am a very good attacking and tactical player. There is just one problem. While I catch combinations that might even require 5 or 6 moves, I cannot find 1 turn ones. Let's see this game I played today:</p>

<pre><code> [FEN ""]

 1. e4 e5 2. Nf3 d6 3. d4 exd4 4. Nxd4 Nf6 5. Nc3 Nbd7 6. Bc4 Ne5 7. Bb3 Be7 8.
Bf4 O-O 9. Qd2 Ng6 10. Bg5 Re8 11. O-O-O c6 12. h4 d5 13. exd5 Nxd5 14. Bxe7
Ndxe7 15. h5 Ne5 16. h6 g6 17. Qf4 Nd5 18. Nxd5 cxd5 19. Nf3 Nxf3 20. Qxf3 Qg5+
21. Kb1 Bg4 22. Qc3 Qe5 23. Qxe5 Rxe5 24. Rxd5 Re2 25. Rhd1 Ree8 26. R1d4 Re1+
27. Rd1 Rxd1+ 28. Rxd1 Bxd1 29. f3 Be2 30. c4 b5 31. cxb5 Bxb5 32. Bd5 Rc8 33.
Be4 f5 34. Bc2 Kf7 35. a4 Rxc2 36. Kxc2 Bxa4+ 37. b3 Bb5 38. g4 f4 39. Kc3 Kf6
40. Kd4 Kg5 41. Ke4 Bc6+ *
</code></pre>

<p>I was white. This is the one I am presenting, but there are many games where I missed 1 turn tactics. Please help me.</p>
 2042: <p>The answer is simple and cruel -> evaluation of the position. Unfortunately, being inactive for 10+ years, I suffer from the same problem so I know what I am talking about. </p>

<p>You will not find a winning move, nor winning lines, unless you evaluate that they are there in the position. That is why you miss those moves -> you didn't even consider that such possibilities exist in the position.</p>

<p>Can you answer me these questions:</p>

<ul>
<li><p>How did you evaluate the position in the game, after your opponent played <code>17...Nd5</code> ?</p></li>
<li><p>Did you even consider <code>18.Bxd5 cxd5 19.Nxd5!</code> since <code>19...Qxd5?? 20.Qf6 Nd3+! 21.Rxd3 Qe5 22.Re3! Qxf6 23.Rxe8#</code> mates? Did you see this line, and if you did why did you dismissed it?</p></li>
<li><p>Why didn't you play <code>19.Bxd5!</code> with the same mating tactic as above, instead of weak <code>19.Nf3</code> ?</p></li>
</ul>

<p>What I am trying to say is that you didn't evaluate the position properly. Maybe you thought it was advantage for White ( <code>+0.80</code> or something similar... ) while I believe it was won for White ( <code>+1.60</code> at least ). </p>

<p><strong>I strongly believe that you would have found these lines on your own if you thought you had a won position.</strong> </p>

<p>Solving tactical puzzles can fix this problem to some extent, but you really need to learn how to evaluate the position properly and this comes with experience. Reading books about typical middlegame positions helps as well, so does strong knowledge of endgames. These will help you in the beginning.</p>

<p>I advise you to start with tactical puzzles, and then move towards typical middlegame positions.</p>
 2001: <p>It is a common problem to calculate all the variations and then suddenly realize that the first move was simply terrible. Actually, there is a rule that should be applied after finishing a complicated calculation, the Blumenfeld rule!</p>

<p>The Blumenfeld rule is formulated roughly as follows. After finishing a complicated calculation, take a fresh look at the position on the board. Try to picture the position directly after the next move you plan to make. Check whether you are missing something trivial. Are you perhaps losing a piece after this move? Are you missing a simple check that makes you lose material? Perhaps you will even be checkmated in a few moves? Only after completing this check for terrible blunders can you now go on and make your move.</p>

<p>This rule does not come easy to any player at any level!</p>
