In addition to being a positive experience, your exercise regimen should take into account your goals, whether they are burning off pounds or building muscle. In addition, whatever the choice, it needs to be something that can be done routinely - so climbing Mt. Everest doesn't count... If there are too many obstacles, then you won't do it on a daily basis. And it helps to actually have multiple activities so you can mix it up a bit.
While running seems to be at the top of the list, it doesn't work for me. My brother on the other hand has been doing it most of his life and gets a mental and physical boost every time he hits the street - like everyday. In my case, due to several knee operations and minimal cartilage, I am not supposed to run. Doesn't mean I can't do it (what's a Doctor know anyway) but I took up walking instead, which eventually turned into power-walking.
For some reason, walking isn't taken all that seriously in terms of health and fitness, yet studies show that power-walkers like myself burn as many calories as joggers, plus we tend to go further which means even more benefit.
I know a lot of runners who are happy to do 3 miles in 20 minutes. I can do 2.5 miles in 30 minutes and routinely go 5 to 6 miles total. BUT, I didn't start at that level. Used to be 15 minutes on a treadmill (yuck) 3 to 5 days per week. I made the same classic exercise mistake initially by using a treadmill - I hated it!
But it all turned around when I moved outdoors and begin hunting for walking opportunities with a view, which made it interesting and fun. And when I travel, walking becomes a mechanism to see new sights from a ground level perspective. Plus walking can be done anywhere anytime, and even at moderate paces, its quite healthy.
OK, so running and walking isn't for you. Fine. What does sound interesting? Sadly, activities like chess don't burn many pounds, but swimming and tennis do. And beach volleyball - one of my favorite Olympic sports - but it requires a beach, or at least sand... So, make a list of activities and do some research into the benefit and calorie burn for each. Target things that make sense for you and look for variety so you can keep things fresh and fun. Power and stand up paddle boarding are my main "workouts" and I look forward to them such that I don't need motivation to get moving.
For the most part, the only time I have needed motivation is when I was battling pnuemonia, and beleive it or not, I got in my walking every day, though at a reduced pace. So the next time you start to dread your "workout" don't look for motivation, look for a new approach.