Lots of good advice here from Job and Toots, not forgetting 25years and her amazing list of GAL.
By my own experience, it is hard at the beginning, but then it start getting easier and easier. You need to expose yourself to the new and that is a bit uncomfortable at first.
But believe me, it gets better and makes you feel really alive again. It does not mean that you will suddenly resolve all the issues and just forget you H is even there.
Every time you do something, you will think about him being there. With time, you start changing that, and you will think that you and only yourself are enjoying your new activities.
The more you expose yourself, the better is a chance to meet new people, expand your circle of friends and have more opportunities to have some good time and fun.
I still go up and down, back and forth, but things are changing inside of me, and I am feeling a little better because I have been finding myself again, and it is getting easier too. I am more confident now then I have been for the last ten years.
25years gave you (and me) good advice that reach the bone core. She was very right and it is worth to follow it like a bible.
Try it small at first, if that is the way to start somewhere, you will feel better, I can assure you.