You are not alone. Lately, I try to do a last minute safety check, which often reveals what I'd forgotten.
It's the thinking pattern I need to adjust I guess. On a humorous note, yesterday I was playing on my phone on chess.com and meant rook to say g6 and by mistake I hit G5 losing me the game! I wasn't pleased at all :) !
Chess requires a disciplined thinking pattern. Two steps towards a disciplined thinking pattern are:
1. Sit on your hands when playing a game. This will require that you play standard time control games of 2 hours or more. Playing rapid transit games is harmful to your game at your level. If you would like to know why strong players play rapid transit please let me know.
2. Write a Before I Make A Move List. Check each item on the list 2x before making a move. An item on that list should be: Do I or my opponent have an undefended piece or pawn in the present position or in the position after my move. After repeated use of the list you will have memorized it and it will be your thinking pattern.
Two hour games are long . You can sit on you hands on shorter intervalls as well. I get that pros counting ten moves ahead need that much more time, but even Carlsen said "if you see me thinking for more then 10 minutes there is a big chance I already found the move, but I keep thinking in sirkles only harming my own game" (its translated, but you get the idea".
A big part of a neb playing the game is "feeling" where the pice should go, start to think and you may beigin to make moves to clever for your own good. Once in a otb match I found such a beutifull fork between the queen and king I missed a mate in two. If I had continued to play "dumb" I would have won.
I have become a strong believer in this.
I just recently began playing 5/0 games and I am always seeing things I learned from my play in Online Chess.