Most people quit the gym and exactly the wrong time. They stop when they start feeling progress! Why??
Think about the hardest thing about learning to ride a bike...it's the change in velocity. It's the moment when the wheels start turning, faster and faster that all of a sudden you start thinking "NO, STOP, ABORT!". Getting on the bike is fine, it's when you start gaining momentum that your brain freaks out and often you fall or jump off just to get back to safe ground.
I think there are similar sensations and reactions with making progress at the gym. It's a paradox of sorts. We join a gym to benefit from the momentum of good feelings, the coaching support, the peer group, the competition, the catalyzing of new habits like sleeping more and eating better, and the corresponding dropping of habits associated with sedentarianism (snacking, lounging, excessive social media).
In a lot of ways your identity has to shift and it's exciting for that reason.
But as the skateboard wheels are speeding up, or the bike starts heading downhill, it's natural to get scared. The part of us that senses change coming, resists. When we were kids, that was the MOST dangerous time because that's when you fall off and scrape up your knees!
We know now, as adults, that you can't ride a bike without accepting the speed and momentum as part of it. You can't ski without leaning forward into the hill - leaning back is disaster every time. You can't surf without accepting the speed of the wave (I can't surf btw...I tried to learn but got absolutely whomped by the waves).
So be aware...when you come to this gym, you will experience a change in velocity. You will feel a change in momentum that can be scary and unsettling and you'll want it to stop. But I promise you, if you lean into it, you will find a new "normal" pace, and you'll see that you can actually find greater freedom and joy in attaining balance and control at speed.
Why do it? The text book answer is that you move into a lifestyle that promotes strength and longevity and all the proven benefits of pursuing activity.
But also, why did you learn to ride a bike? Because you can. Because not to is an insult to your capacity as a human being.