‘Negative’ divorce – genuinely grieving or indulging

I went through a divorce last/this year. July 2017 – the idea appeared, Nov 2017 – it became a certainty, March 2018 – officially divorced.
It was a total surprise to me. My ex-husband kinda just left.
I realize I’m in that phase trying to feel good about a ‘negative’ circumstance.
I want to give time to myself to grieve, to allow the feelings, and not try to brush it off.
At the same time, I don’t want to indulge in negative feelings, in ‘poor me’ kind of thoughts.
How do I deal with this? Just decide to give myself a timeline? How do I know I genuinely need more time to grieve or I’m starting to be indulgent?