Help ! I suck at chess.

Ive been playing on chess.com and have around 100 plus games with mostly bots around 1200s. However, when I play 10 min blitz humans, i lose 90 percent of the time. I am stuck around 300 now. I do not feel like a beginner. I do daily puzzles and lessons and am on advance. Should I just quit considering I might not have the brain for this game? Any advice?