How to Stop Blundering in Chess
You stop blundering by finding the blunders you repeat, then practicing those exact positions until the safe move is a habit. Random puzzles help a little; your own repeated mistakes are where the rating points are.
Why blunders repeat
A blunder is rarely bad luck. It is usually the same oversight in a new position: a piece left where it can be taken, a fork you didn't see coming, a check you missed. Because the habit is yours, it comes back game after game until you train it out.
Step 1: find the blunders you make most
Look across many games, not one. Reviewing a single loss shows you what went wrong that day; looking across your last 25 games shows you what keeps going wrong. Group your blunders by kind and count them. One kind will usually stand out.
Step 2: run a safety check before every move
Before you play a move, ask three questions:
- Checks, captures, threats: what can my opponent do after this move?
- Is anything left undefended? Look at each of your pieces: can any be taken for free?
- Did their last move change anything? A new attacker or a piece that moved away from defending.
It takes seconds once it's a habit, and it catches most one-move blunders.
Try it on a real position. In this game White, a pawn up, played Rxh7 and lost the knight on c4 to a pawn. Run the check first: what can Black take?
White to move
For a coach's walkthrough of these habits at beginner level, IM Kostya Kavutskiy's video is worth the watch:
Step 3: practice your own positions
Take the positions where you blundered and play them again: find the better move, then keep playing until the position is won. Practicing the exact situations you get wrong builds the habit where you need it.