It happens :) I spent 1.5 days on level 23. And now stuck on level 35 for 2 days. Sometimes things are really very simple, but we complicate them. Sometimes we make mistake while typing the answer, like I did on level 26. That extra space in my answer took my whole day.
edit : also the fact that I complicate every thing*
edit 2 : yeah I complicated it
final edit : if I cant make level 23, I should just stop, take a break or smt like that