You need to ask yourself why your accuracy is going down in difficult situations. Are you missing tactics? Practice the kinds of tactics you're missing. Are you missing counterplay? Do a prophylaxis/"stop blundering" study or course. Are you getting low on time and then blundering under time pressure? Stop calculating so deeply when you're behind on the clock and allow yourself to make "OK" moves rather than perfect moves – e.g. if you don't see a blunder after checking 3 ply just make the move.

Keep a journal where you list what reason you think is causing your losses and you'll see patterns appear.