As others have said, caring less about what others think of me.

This means, even though I've only been in my current role at work for under 2 months, I'm already one of the most vocal and outgoing to the point that my line manager already didn't know how long I'd been there as it felt like ages and I was already part of the furniture.

Also financial security, house(s), pension/superannuation, kids etc.

Need to get back to the gym a bit more though - have a home gym so no real excuse other than being a bit more tired as metabolism has slowed but it ramps up quickly enough within a few weeks of being back at it and that helps with all general life tasks. So you feel more awake and stronger and being in your 40s, you really notice the difference, unlike in your 20s.