I went through this when I quit caffeine. I had been exercising nearly daily for two decades, loved almost every second of it, literally always caffeinated. Then I quit caffeine for digestive reasons and my god it's like any form of exercise is pure torture. Finally starting to come through the other side, had to drastically simplify what I was doing to make it palatable (basically just running + yoga at this point.)

I was you once. Once I achieved a high level of fitness and a motivation to push the limits, then I understood what people mean when they say exercise can make you high.

I'm still like that -- sort of. I'm a busy dad of three active kids and have always been athletic and active, but sometimes family obligations prevent consistency for periods of time. When restarting from a low fitness level (whether, in my case, it's cycling or running) I always feel demotivated and pretty crap until I'm about 3-4 weeks into a regular (5+ day/wk) routine and have built my aerobic capacity back up to a point where I actually feel like I'm really running (or biking) again. It's demotivating for the first few weeks, but I've been through this routine enough times to know the light at the end of the tunnel isn't very far away. I think a lot of people who don't have athletic backgrounds and are just starting their fitness journey are mentally hampered by not knowing how the journey progresses, and when they can expect to start feeling and seeing changes. Also, running is non-trivial. People assume it's a natural movement pattern for humans (and it is), but it's definitely not for adults who live largely sedentary lives and are not already fit. It can be downright dangerous if not approached carefully, especially compared to lower impact aerobic activities like cycling & swimming (or elliptical or stairclimber).

tldr: people who never push themselves will never likely achieve an exercise high. Also, people starting at 0 have a much harder slog of it than those with a decent base & athletic background.

Try different exercises. I abhor running, but love swimming, for example. Group sports are more appealing to some people. Small groups, like padel, pickleball (never played) or tennis (love it). Large groups, like indoor soccer or volleyball.

To each its own, but don't lump exercise into a single class. Try some variety!

Agreed. Pure agony. Afterwards I am so exhausted that I often find myself at the edge of tears. Worse it seems to turn off my immune system and I often get sick.

But I do have a clearer head for a few hours after a run so I keep doing it.

I only experience this with high intensity and when I'm out of shape. Consistent moderate exercise makes me feel pretty good.

It changes once you get half decent at it.

The problem most people (in my experience) have is that they don't actually start training with any intention of becoming half decent, which both psychologically and physiologically limits their potential outcomes.

This is a silly stance and honestly condescending. Not everyone works the same way you do. I've competed at the national level and I often find the workouts strenuous and boring, not fun. Projecting your own experience onto others is a great way to demotivate, not help them.

Find something that you enjoy. I hate running but I love boxing.

I'm the same. Running just to run is agony. If I'm playing a sport, then I hardly notice it. Jiu jitsu is my workout of choice.

Do you like moving in general? Find a ninja warrior training gym or a trampoline park.

You may be ramping up too quickly. It doesn’t need to feel like torture. Drop any preconceived notions of what counts as an “exercise session”. Go as slow as you need. Let your body adapt.

When I first got back into running 2 years ago after a long hiatus, I had to learn the painful lesson that I was being way too hard on myself. I eventually figured out that I can slow down and start with just a very slow 0.5 - 1 mile jog. I can even stop and stretch in the middle of the run if I'm feeling tight. It sounds silly, but I didn't realize that was allowed. There are no rules. If anyone judges you, that's there problem. You do you.

Here’s one of many, many possible examples:

* Walk for 10 minutes 3x a week for a few months.

* Walk for 15 minutes 3x a week for a month or two.

* Walk for 20 minutes 3x a week for a month or two. Stretch for 5 minutes before or after walking.

* Walk for 5 minutes, then jog VERY SLOWLY for 5 minutes, and then walk for 5 more minutes. Stretch for 5 minutes before / after.

* You get the idea…

And if running isn’t your thing, try something else. The only that matters is that you move and use your body. There are a million ways to move the body! I bet you can find one you like :)

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More philosophical / technical approach:

Treat it like a puzzle. You have a System in State A (your body and your current behavioral patterns).

How can we get the System to State B? Or wait, perhaps State C or D are just as good or even better! We just didn’t realize those were possibilities.

Consider dropping old assumptions. Experiment! Try different things :) What are different ways of interfacing or evaluating the system? Perhaps some of the old interfaces and metrics aren’t as useful or applicable to the current state?