My recommendation is to take time every move. Think for as long as you can stand it and then think longer. Once you've moved your piece with the mouse take a quick glance over the whole board before clicking the submit move button.
Correspondence allows you to think a lot before you have to move. There is no excuse for not looking at every check, capture, and threat that you or your opponent has.
When I play fast (like I did the other day) I blunder (like I did the other day by allowing my bishop to be trapped by a pawn)
1100 Or 1200 rated can be the toughest to beat. May be I am going through lean patch these days.Out of form,disturbed or over confident or what?.