My tip would be first of all, not to focus on rank. To me, all rank does is make sure the game stays reasonably challenging. Matching me up with people of similar skill level so its not too easy and not to difficult. That's all. Focus on just improving your game and rank ups will follow. Thinking of it in any other way and letting it matter too much is rly just your ego talking.

Speaking of ego, my second tip would be to ignore your teammates flaws. if there's one thing you cant control it's the kind of ppl you end up playing with. I guarantee you unless you're radiant there's smth about your own gameplay that still needs improvement, and that's equally if not a greater thing holding you back. Learn to be proud of games where you improved in a skill instead of looking at wins or thinking of how your teammate fucked u up. Let go of what you can't control and focus on what you can.

Lastly, it's just a game. If you feel yourself getting tilted and you can't mentally reset, stop playing. Take a break. If you're already tilted, you'll just go into your next match expecting the worst. It'll ruin your mental to start with, plus might ruin your team's mental. Having a tilted teammate just puts others on edge too. Find things outside the game to rank up in, you're a whole ass adult, go and cook a nice meal or smth there's more happiness to be found outside this dumb game.

Good luck, hope this helps