How can I distinguish seen videos from unseen ones on youtube account?

I want to distinguish those videos that I have already seen from those I haven’t. Its such a waste of time to see the same video again and again.Can I do something like ‘mark as watched’ (not exactly this) thing so that I know beforehand I have watched the video before it starts buffering.If I search for some keywords I get the same videos that I have seen earlier along with others in top results,it becomes confusing and irritating also.
Any idea how to do this?