Setting aside for a moment that he sounds like a bit of an inconsiderate jerk (who leaves their SO behind??)...

Okay, thank you, this is what I was thinking half the time. I've experienced him not waiting for me during activities a lot over the years, so I've gotten more dismissive of the behavior and just started thinking it's something I can't change. But it really does irk me that he does it.

Idk how that would work for adults, but you might make a game of it. Tell him to get to the end as fast as possible and then see how fast he can get back to you, and back and forth that way. If you're on city streets, have him detour around a block and see if he can beat you to the next street while you go straight. Hope that helps.

This is quite helpful, and I had a similar idea. Maybe I can leave 20 minutes earlier than him and see how long it would take him to catch up. But still, it makes it all about him, you know? Why can't he be more understanding toward me? Like it's such torture to slow down a little.

Also, tell him he's being an inconsiderate jerk.

Oh I have before. Sometimes I feel more like his mom than his wife, and like I have to reprimand him for dumb behaviors. He's the middle child but first son, and it's kind of known in his family that he's the 'favorite son' (a little fucked up, yes.) So he has a little bit of a big head sometimes when it comes to thinking he's special and the best. It doesn't help that he's often stronger and faster than everyone. He also thinks he's smarter. (He's not... I wrote him the bomb ass cover letter that scored him both of his current jobs). And I think his Momma's Boy syndrome often leads him to acting like ways he plays off as 'cute' or 'benign cuz I'm just being special me!' but is actually 'inconsiderate jerk.'

We're cool in other ways as a couple, but goddamn he is a damn piece of work sometimes. It makes me so mad sometimes.