When in a "winning position" which there are none... take a deep breath when you have the "advantage". Look for tactics and be vigilant. I would tell you I've won more "lost positions" because I became even more vigilant to win. Stay vigilant to win and keep your mind humble. Its not over till its over and there is no taking a relaxing time when your winning.
Lastly, how are you losing your games; opening, tactics, endgame? This will help guide what is weak in your game other than cognition blunders.
Re-awakening this forum.