?

Sometimes we have to accept that we may never have the answers. We may never understand. 

That's okay.

Closure need not come from resolution. It can come from acceptance. It can come from the passage of time. And in cases where its relevant, it can come from forgiveness.

What you can't do is dwell upon things. Yes, reflection is necessary, but it can become counter-productive if you don't move beyond it. I have witnessed otherwise sensible, intelligent people become obsessively analytical to a point where it has permeated and consumed every aspect of their existence, leaving them mentally compromised and emotionally exhausted (and exhausting).  

I speak from experience.