Don’t give up. That’s what you do. If you have been playing since launch and reached Diamond 1… than it’s just a matter of time before you will hit it. I have been playing since launch and when I decided to actually try for the first time a few years ago, I reached Diamond 3 the first month, and than Hit legend the following month.
When you hit legend for the first time, it’s awesome… and you will get there, trust me.
I decided to grind this month with a Kingsbane Rogue and made it to Legend pretty easily. (Which is funny because I hardly ever play rogue) If you’re having a hot streak, ride it, and if you’re on a losing streak, step away before you lose more because you’re frustrated.
Aside from that, just keep grinding.
Play games that arent rigged instead
Do what I do, uninstall the game, take a game box from Blizzard, spit on it and hope that bad things will happen to everyone in the company, play final fantasy and be happy 
Why are you here in the game forums? Just play Final Fantasy right?
I do…please don’t worry about me…