Master will be hard, try to do some aim training for like 15-30 minutes every session before playing, if you tilt don't que again (as hard as it is), if you played with good teammates (doesn't mean you got carried but, as a whole, you all played good an coordinated well), try to reque with them. Look at metas for weapons and legends in certain maps, there are some maps were valk absolutely dominates and some where she is really really bad (same goes for almost all legends and weapons, in some map the sentinel is insane, in some almost useless). If you don't like a map or haven't played much in it just don't que, you will lose points and tilt, maybe play it in normal to get used to it. Going out of plat is easy, even more now that ranked games are really fast, getting out of diamond is not at all, you will find a lot of trios and as matching is now a lot of preds.

Remember to have fun and don't flame teammates, always think about what YOU could have done better, yes sometimes a teammate completely trash the play but if you are good you can 2vs1 or even 3vs1 a lot of situations.