I have been preparing for the interviews for about four months. After losing my last job, I decided to take a break and prepare for interviews. I can easily find some crappy job in another super-duper startup, but I don't want to work for startups this time. So, I scheduled the phone interview, and time is ticking. I solved in total over 400 tasks and kept practicing and reviewing tasks I already solved. Now I feel nauseated and fed up with preparations. I am losing motivation to keep up. I am burned out...

Update: Thank you guys for all your comments! I am surprised by your support. I have said that I solved around 400 issues, but it is a number of submitted issued. Maybe half of them I could not solve or solved inefficiently. Right now, I look through all of them. In the beginning, I didn't have a good process in revising or making notes about mistakes. Now I meet some tasks which I solved three months ago. What upsets me more, of course, I don't remember the task not to mention the solution. More tasks I try to solve and keep in my head, more I forget. My brain is like a queue with limited capacity. No matter how much I push in my head, the capacity stays the same. Don't get me wrong, I am not trying to give up. It is just my brain resisting to accept new data.