That all depends on how, and the context in which it’s done. My first girlfriend would spend hours tickling my back in between sessions - I never forgot those sunny days.
Now with more aggressive tickling - it is akin to a violent attack, and my father used to tickle me until I couldn’t stand it, and then push some more. Often it ended with me in tears… so with my son, sometimes I’ll grab a foot and start tickling it like mad - but I have a MUCH shorter cutoff time so that it ends with him laughing.
So it’s not simple - but consent is a huge issue.
There are a couple of things here… firstly you’re thinking about him being with someone else - that’s not just a ‘breakup’, that’s worse.
Anyway, I found relaxing to be difficult so I went out and did stuff - also I just met lots of friends and tried not to be on my own. During my last breakup, I had someone to meet every day after work for a week - and that put some distance which made it easier.