I think most of us have to find ways of not getting too aggressive and not defensive enough when we are winning. The best way to keep an advantage is to practice Nimzowitsch's "Overprotection" - making sure you pieces and weak squares are guarded.
Of course, if your opponent has a material superior on an important part of the board, your overall material superiority may not count for much and you may have to make risky moves to overcome the problems that arise.
I think most of us have to find ways of not getting too aggressive and not defensive enough when we are winning. The best way to keep an advantage is to practice Nimzowitsch's "Overprotection" - making sure you pieces and weak squares are guarded.
Of course, if your opponent has a material superior on an important part of the board, your overall material superiority may not count for much and you may have to make risky moves to overcome the problems that arise.
It happens more often than not in endgames. I can nurse an advantange through the middlegame, but when pieces start coming off and I think that there is a critical line, I rush into things without looking.
There is also Steinitz's Principle of Attack: "The player with the advantage is compelled to attack proportionately to said advantage, or he runs the risk of losing it."
A balance between the two is nessecary... I'm looking for a way to remind myself to hold my horses and use rational thought. 
Thank you, your advice was useful!
Yep... I will have to start thinking that way
I learned something very important from a Danny Rensch commentary that I've committed it to memory:
"When you're Winning, it's only Beginning!"
Getting a Won game is different from actually winning a Won game.
Yep. One of the reasons I gave up OTB tournaments. Too careless, too quick to move, not seeing the whole board. One idea is to create a mnemonic, so that you check 5 or 6 things BEFORE you make a move.
I thought that you start blundering when you are losing, not wen you are winning.
Hello chess.com!
I have a big problem in my thinking that has resulted in my losing the last 7 OTB games that I have played. In all of them, I get into superior positions, and promptly get excited, and start tunnel-visioning, usually resulting in me falling for a silly, obvious tactic, and missing my own better opportunities. I have a statewide tournament starting tomorrow, that I don't want to make these sorts of idiotic mistakes in my winning positions.
A possible solution that I have thought of is simply not to consider positions won, but of course, this is easier said than done.
Has anyone had this issue, and what have you done to rectify it? Also, how long did it take you?
Cheers!
Willy