I've just turned 30 and I used to do a lot of cardio exercise. Over the past few years as other things have taken priority, I cut back. I'd try to do something every day but would often miss days and the workouts would be short and poor quality.
After getting (fortunately mild) COVID I was worried about cardiac issues when I resumed exercise. I decided to buy an Apple Watch to monitor my heart rate and use the ECG functionality.
A few months later, and the big thing I have learned about myself is how well I respond to "gamification" of habits. I now HAVE to close my exercise rings every day, and it's immensely gratifying to track my overall health improving - I did not realise how out of shape I really was. I'm sleeping better, a lot more productive, my mood has increased significantly, and overall I feel much better in myself.
It's also lead to me using other "habit forming" apps (I use "Streaks" - https://apps.apple.com/gb/app/streaks/id963034692) to change things I don't like about myself and generally become a better person.
Overall, I've learned a lot about myself and how I'm motivated.