Can I say “grow the fuck up” to a friend?

How much can you push the “politeness” boundary to a friend? I find myself to be someone that cares a lot about people, especially friends. So I introduce to them an opportunity that I know they will excel in, and beyond that love it at the same time.

Then they flake, then they give excuses, all the while banking on my passion and energy to help them along the process.