I made so many of those mistakes, particularly buying this one shit coin at an all time high. Thats the one that has hurt me the most, the most painful, especially putting everything in it, committing another bad mistake in not diversifying. So many mistakes running through my head.
I believe mistakes are really unavoidable especially if you're still a beginner.But do not afraid to commit mistakes because this will mold you to be a good trader in the coming days.I think the ways posted above are very helpful but i'm sure you will not understand those things if you never tried trading with big losses at first.