The problem you have that is holding you back is your mindset. You are so fixated on diamond 5, maybe you feel like d5 is really good players or something. Focus on improving your game play more to a master tier level(obviously easier said than done) than worrying about winning a couple games just to get diamond 5.
I get that it's a big milestone. It is. You should be excited about hitting it, your approach seems wrong though. Think about the JOURNEY not the destination, you will climb because you're truly a diamond skill level and not just because you got a little lucky.
Remember this, the game play difference in skill between p1 and d5 is nil. You've reached high plat, almost d5, it's time to really take a look at refining your game play, not making those dumb mistakes that you know you make every game but do them anyways kind of thing. Shoot for playing the game PERFECTLY and you will just keep climbing.