user25128: I'm fairly new to chess. I'm practicing against 1500~ rated opponents/engines on chess.com. My openings and middlegame seem to go well. After every game, the engine analysis says I'm always up +1 ~ +3 for the majority of the game. But at the end, I always seem to lose by a blunder. Every game is a "giveaway" according to the analysis engine.
It seems my trouble is actually converting positional advantages. Do you have any tips or areas I should study to avoid this? Is this a stamina issue, as in I start to lose concentration as the game goes on?

user4418: 
Is this a stamina issue? (as in I start to lose concentration as the
game goes on?)

No. If you are consistently reaching the endgame then it is a "lack of endgame knowledge" problem.
Do you know when KP v K is a win and when it is a draw? Do you know how to win the Capablanca pawn endgame as white? Do you know what you have to do as black to draw (if white goes wrong)?
[title "Capablanca Pawn Endgame"]
[fen "6k1/7p/8/8/8/8/6PP/6K1 w - - 0 1"]

In short, do you actually know how to win a won endgame when it isn't just trivial?
If you are not consistently reaching the endgame then you need to work on tactics.
Actually, you probably need to work on both endgames and tactics.

25128: <p>I'm fairly new to chess. I'm practicing against 1500~ rated opponents/engines on chess.com. My openings and middlegame seem to go well. After every game, the engine analysis says I'm always up +1 ~ +3 for the majority of the game. But at the end, I always seem to lose by a blunder. Every game is a &quot;giveaway&quot; according to the analysis engine.</p>
<p>It seems my trouble is actually converting positional advantages. Do you have any tips or areas I should study to avoid this? Is this a stamina issue, as in I start to lose concentration as the game goes on?</p>
 4418: <blockquote>
<p>Is this a stamina issue? (as in I start to lose concentration as the
game goes on?)</p>
</blockquote>
<p>No. If you are consistently reaching the endgame then it is a &quot;lack of endgame knowledge&quot; problem.</p>
<p>Do you know when KP v K is a win and when it is a draw? Do you know how to win the Capablanca pawn endgame as white? Do you know what you have to do as black to draw (if white goes wrong)?</p>
<pre><code>[title &quot;Capablanca Pawn Endgame&quot;]
[fen &quot;6k1/7p/8/8/8/8/6PP/6K1 w - - 0 1&quot;]
</code></pre>
<p>In short, do you actually know how to win a won endgame when it isn't just trivial?</p>
<p>If you are not consistently reaching the endgame then you need to work on tactics.</p>
<p>Actually, you probably need to work on both endgames and tactics.</p>
