alright i ll give you some tips based on my experience:
If you are on a winning streak (3 games+) and you lose 2 games in a row after, you stop playing for the day.
If you lose the first 2 games in a row, take a break and play one more later, if you still lose stop playing for the day.
Download pro matches and watch them on GOTV, figure out your role in the team you are playing and adapt to it ( lurker, support , entry fragger , IGL or Main AWPer)
play every single map and learn them.
IMPORTANT ONE: If you are playing a game and you see yourself on fire, DO NOT STRETCH YOUR BODY DURING THE GAME; it affects your aim,reflexes and gamesense. Once you are in the zone don't break from it.
optional one: skins actually changed the gameplay for me especially knives, I felt the game more fresh and colorful which helped me focus more.