I’ve never had trouble playing games against myself. Obviously, you can’t do this very well with games that have secrets (card games, battleship, stratego, etc). And you know what the other side is trying to do, so you won’t surprise yourself (although when I was a rookie back in the day, sometimes you can. When you go back to playing the other side, you may notice something you hadn’t before, and BAM - you sink their transports or attack their vulnerable bombers or bomb their defenseless factory).
You want to get better fast? Play against yourself. You get to take every turn, and look hard at your opponent’s perspective on your own play.
Also, if you’re a rookie, you save yourself the embarassment of others seeing your pathetic missteps. :lol: