Try to just track the straight 1v1 fights in your dms. Don't try to win. After every death, if you were double peeked or shot in the back, just try to ignore it (can be hard, I know); and if you lost a straight duel, ask yourself why (was it movement, was it aim, angle disadvantage, peeker's advantage? Something else?) and keep track of your mistakes. If you make certain mistakes more often than others, try to run a DM while only focusing on that stuff.
If you hyperfocus on small errors and trying to get better at very specific things, you'll often notice visible progress, even if you continuously get shat on. For example, my problem was that I often pressed W while peeking, so I double bound knife equip to the W key and focused on swinging with A and D only and strafing during fights. I didn't do well in the DMs kill-wise, but after a couple of them I noticed I was getting a lot better at horizontal movement, so it still felt like a success and I didn't really tilt much.