Though I think it's admirable of you to be able to say that, one could rephrase "You've wasted your life. Nothing of what you've done is relevant or useful." since it seems - at least to me - harbor something a moral along the line of "how could be so stupid to dedicate your life to something as useless as . . .". Something that I don't think is true.
It's just occurred to me that, giving all the cheerful risk stuff I work with, one of the most optimistic things people could say to me would be:
"You've wasted your life. Nothing of what you've done is relevant or useful."
That would make me very happy. Of course, that only works if it's credible.