My interest here is simple. I want to deepen my knowledge of English (and amuse myself a little) and I guess this issue is going to help me. There's definitely some interesting points here. I think we have at least four words here which I take perfective whereas you don't. The main thing here is that they all in the Future Simple tense, i.e. Sth+Will+Verb formula. I take it for granted that you know your native language better and I can rely on your knowledge. So it's time to say:

Wtf!? How do you guys decide between momentary (instantaneous, instant) and ongoing actions in Future Simple? How do you get that "I'll face it with a grin" is an ongoing action? Why not a momentary?

Also:
Whatever happens, I'll leave it all to chance
Another heartache, another failed romance
I guess heartache and romance are things that are going (among others) to 'happen' there; they may happen maybe once and maybe more than once. That's why 'happens' and 'leave' are imperfective. Am I right?

In case of Russian, we have a perfect tool to underline whether the action is instant or ongoing, which is aspect.