How to prevent blunders?

Every time you blunder, cut off a toe. Then a finger. Then every expandable appendix. As you'll threaten to amputate some vital organ in turn, your brain will understand it's serious, and will eventually pay more attention to what is going on. Simple.

there's nothing you can do.

Grind through thousands of tactical puzzles until you have better "board vision"

Father-son conversations are so awkward ...

hahahahahahahahaha.....

It is impossible to prevent them completely, we are all humans after all. Even world champions blundered pieces.

Slower time controls might be boring but, at least you learn to play chess.

Bah, anyone knows after experiencing it, slow time controls are not boring when you play OTB in an official competition: you don't "see" time anymore. No joking.

you never can learn chess, so even being less stupid is not good, and if we can never be good, let's have some fun.

Training tactics should definitely help.

Besides the obvious points of focus and studying tactics, I find that my most likely time of making a blunder is immediately after I made a blunder or my opponent makes a move which surprises me.  And, I think this is true regardless of skill level.  

Let's say you drop a pawn or your opponent plants a piece where you didn't expect it...I find a lot of the time, this is when a bigger (fatal) blunder can happen.  When you make a mistake, be very careful because mistakes can come in bunches when the position changes dynamically.

This also works in reverse when you are playing.  Assume your opponent loses the exchange.  Look a little deeper after he replies, and you may see he hung his queen (or king).

Let's blunder those tittiies

You either learn from your mistake or when you blunder you keep calm and play. You can never fully stop a blunder but that makes a human a human you'll always have a brain fart no matter how hard to try even at the professional level you make a blunder.

@SonOfThunder2 how many fingers/toes you have now.

Alternatively, aim at your own head with a gun, and tell your brain: "Listen you idiot, if you blunder again, I'll shoot you!". If it doesn't work, shoot several times. You don't want to miss the tiny little basterd giggling up there.

There is also the fact that many people tend to make very specific blunders repeatedly, corresponding to particular weaknesses in their intuition and board feel - once you've learned what blunders you tend to make, you can target them specifically.

For example, my weakness has always been the horizontal vision: in 90% cases, when I blunder something in blitz/bullet, it is because I missed it being defended by a queen or a rook horizontally in a hasty calculation. I am now working on solving a lot of tactical puzzles involving horizontal ideas, and it is improving the precision of my quick calculations rapidly.