Psychology
This game has a surprisingly significant psychological component. Tilt is the SR killer. If you find yourself yelling at your teammates (either over voice or internally), yelling at matchmaking, coming up with elaborate theories for why you are not the one at fault for your rating, take a break from competitive. Play quick play, arcade, a different competitive account, or some non-Overwatch activity. Don’t come back till you feel better.
Acknowledge that you are bad, and the only way to rank up is to get better. “Get good” is not a toxic statement. Getting good plus enough games played is how you gain SR.
There will be times when you lose many games. On one hand, it may not seem like your fault. There were leavers, trolls, attack Torbjorn’s, etc. However, if you were good enough, you would not have lost. You put any Overwatch League player in that match, on your account, and they would not have lost any games in gold or below (and lose very few in Masters and below).
SR is only accurate to +/- 250 in ordinary circumstances, and +/- 500 in extreme circumstances. Don’t take the slings and arrows of outrageous SR fluctuations too seriously. As your SR drops, think, “Hey my games should get easier now, good!” As your SR rises, think “I’m getting tested, I need to step it up!”
Patience is key. It took me two years, three months, and 555 levels to make it to platinum. Each transition bronze -> silver, silver->gold, and gold->plat had multiple false starts and setbacks of hundreds of SR before I broke through for good. Now, if you are younger than me, can train your reflexes faster, and have more time (I’m a forty year old dad gamer) you can do it faster, but still: expect it to take a long time.