One thing I noticed is that whenever I make a really bad blunder, I'll usually see it almost immediately after I've made the move... too late to prevent disaster, of course, but...
Here's a trick that I used to use in over-the-board tournaments.
After I've decided on a move but before I actually play it, I will first compose a little mental image of myself reaching forward, making the move on the board, writing it down on the scoresheet, and then sitting back in my chair.
Quite often, I will suddenly spot the blunder at that point... in that little moment of relaxation that comes with the dissipation of tension "after making my move". Although of course, since this is just a composed mental image, I haven't actually made the move yet... or even touched the piece. So it is easy to wipe away that mental image, recalculate, and decide on a different move to play.
Any hints on avoiding blunders? I practice puzzles and take lessons but when playing daily games (and there is no rush) I continually make stupid blunders giving away pieces. I take my time but somehow immediately after moving I see my horrible error.