Hello Lonely Girl
I agree with Alexlisa about coincidences. Even when we know it's coincidental it still gets under our guard and messes with the brain. You know about the earworm? When you cannot get a song or piece of music out of your mind and no matter what you do it keeps coming back. Sometimes these reminders can be a memory worm. Not sure if there is an expression for this. Anyway it just keeps burrowing.
It will eventually disappear but so frustrating while it is with you. I wonder if making a constant effort to think of something happy, not to do with ex, could be helpful. Alexlisa has suggested various activities and this is good. Sometimes a more physical activities can help. Something like gardening or going for a walk, meeting some for a catch up and coffee. I'm sure have various strategies up your sleeve.
May I ask, what is PDD? I don't recognise the initials.
That feeling of your mind going in circles and losing concentration is familiar. It helps to do something that you know very well. Walking is almost doing something on automatic pilot. It does help by releasing hormones into your system which can lift your mood. You are also working on your fitness as a bonus. 🌻
I have found this is the trick to keep my mind in order, do something familiar but still needs you to be involved. Remember you are always welcome here.