I used leetcode to execrise for more than two years. My attitude changed a lot from the beginning.
At first, I felt the problem is really hard. It's true that doing the exercises sometimes is a torture for me.
As more time I spent on the LeetCode, I found the problems on LeetCode is actually about proficiency. The problems in the LeetCode usually are clear for the special algorithm. If I felt hard of a problem. I will just watch the explaination and try it again and again. Make it as my instinct. And after a while, I just find I can deal with the similiar problems.
This is what just I thought, maybe I am wrong.