The other day at my local health food store, I was settling up with the cashier on a canister of protein powder. They asked what I did as a workout and I told them that I was a cyclist. And after a few moments of describing some of that, they asked me what they could say to their partner to get them to start working out...
From time to time, I'll get asked this sort of question: someone/someone's partner wanting to get motivated to get into shape and seeking out some magical nugget of advice that'll just mentally lock into place and ignite their butt. I'll impart something, but whatever I say won't and doesn't ever land. That's not how motivation works. Motivation, in the context of exercise and staying healthy, works by basically having your life seriously held hostage by heart disease and diabetes. If the grim reaper hasn't asked you to sit down for a coffee to "talk", nothing else is going to motivate you to keep fit.
But I'll take a breath and park my high horse and say some shit that sounds like it's worth a damn to consider. And usually, it goes to the tune of this...
"Getting fit or staying active doesn't have to be tethered to running and weights. That's not fun or motivating, that shit is boring. I don't know how running and weights became the one and absolute standard of keeping fit. I hate those two things, I especially hate running. What is it that you've ALWAYS wanted to do? What is it that you've seen and makes you feel jealous or envious that that's not you that's doing that? Pick something that looks and seems REALLY fun, it could be kick-boxing, it could be rowing, it could be fucking lawn bowling. If it seems like more work than fun, ditch it. If the thing you chose doesn't work out, move on to the next."
Additionally, once you've found your "thing", try to make a habit out of it, like grocery shopping. And set a really tiny, easy goal. Then set the next tiny, easy goal. Then keep setting tiny, easy goals until: a) it's no longer challenging and you feel the need to have to set a more moderate goal and; b) you can look back and see that you've amassed a lot of completed goals, which will fill you with a sense of achievement. Add that to the results that you're maybe starting to see and this will motivate you to keep going.
No one is asking you to set massive, insurmountable goals, like scale Mount Killaminjaro in two days. That's stupid. Keep it realistic.
Here is Mark Manson's same take on 'EXERCISE' (scroll down, the section is itemized as '1. EXERCISE')
Good luck, Godspeed, find that trove of endorphins.