Moving forward after a failed relationship is so difficult! I understand what you mean about thinking about it in the mornings and at night. Those times do seem to be the most difficult because you are not distracted by the noise of the day.
I would agree that you find activities for yourself. Also, do you have any pets? They can also be a good distraction and give you unconditional love. I force myself to take the dog for a walk when I need something to distract me or lift me up. The dog and the fresh air are good.
Also, I normally block exes from social media, so I am not tempted to see what they are up to. It takes away all of the temptations. You don't need that in your life.
I'm sorry that you are going through this. I hope that you can find some peace soon.