I can't win Rapid

you should force yourself to think and use your time, there’s not point in losing a game with more time on clock than what you started with

I play 15/10 is that good?
Yes. This is the best time control for improvement and I play it too. However, it is important you take your time as that will help you find the best moves in the position. Once i started doing this, my rating went from 1722 to 1776 and it is going to probably improve more. In a position where i found the best move in 50 seconds, i took 3 minutes to make my move. And @medelpad is correct. Sorry for the long yap session and hopefully you can win more games.
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