> Because it’s FUN. I don’t feel like I’m exercising, I’m just having FUN.

First step is throwing away the idea it has to always be fun. You even said right before this:

> And even the days I didn’t felt it, I never regretted going for it anyway.

So it's not always fun and you always don't feel like it, but you connected it to other side of not regretting. That's discipline. The next step IMO, is to embrace when it sucks. Look at the upside that you're not only exercising your body, but also exercising your discipline when you don't feel like it - good for you!

A small example of embracing when it might suck is to not avoid rain. Instead of running, embrace the rain. Relax, smile, and be ok with getting wet. It's temporary. Same thing when you don't feel like doing something you know you need to do, like exercising.