I have been preparing for SDE interviews for last few years. Failed in last 40 interviews.

1)Before phone interviews I memorized important techniques of solving classic data structure problems.
2)What happened in interviews-
3)I didn’t know how to completely solve the problem.
4)Everytime I had a good start but I got stuck on the way
5)got panicked and I didn’t manage to get to a working solution.

Today I feel I am big time loser. And I will never be able to crack single phone interview. But I cannot give up as I need job but I don't know how to successed.