Are we talking specifically about when I committed myself to physical self improvement (lifting weights), or like, more general mindset? I’ll go ahead and answer this in a way that I think answers what you’re asking in a general way, and if there’s more you want to know, feel free to ask 
So, at the very end of high school, and the summer before college, I took an interest in weightlifting. That was the first time I ever lifted a barbell, at the field house at my school. I was so small and weak that it was very difficult to just get started. The empty bar was pretty unmanageable for me. So I lifted a few times with friends, and over the summer I was doing it sporadically.
Then I got to college, and had a real gym to go to for the first time. I started going a few times a week. I had bought the Arnold Bodybuilding Encyclopedia, and was basically just learning from that. My second semester, I took a weightlifting class, and that was the first time I really engaged in any structured lifting, on a schedule. At the end of that semester, I did legs for the first time. And puked. And hated it.
So that’s essentially when and how I started lifting weights. The reason I did involves a couple things. 1. I was unpopular with girls (and really everyone for that matter, lol) , and I wanted to change that. Going to college with a bunch of strangers was the first opportunity I had in my life to make a fresh start, and I wanted to take advantage of that. Arnold was my idol, and I wanted to know what it felt like, what the experience was like of having muscles, of being strong, and physically attractive. I wanted a glimpse into the life of Arnold. So to sum it up, I started lifting weights mostly for the social benefits.
At the same time, I was living away from my parents for the first time, and I was adjusting to the newfound freedom. The freedom to go to parties, make my own schedule, literally do whatever I wanted with every hour of the day. I was working hard to be better at talking to people, specifically women, to be more attractive, dress better, etc. All the things that I thought would improve my life, aside from the gym. I was really dedicated to this, for years and years. It’s a long, hard process to make the changes I did in my life, but I was so deeply unsatisfied with who I was that I kept to it, sometimes off and on, for such a long time.
Certain things were more gradual than others. It wasn’t until my mid 20’s that I really stopped taking long breaks (like a month or longer) from the gym. And that’s also when I became really dedicated to making true, consistent progress, for years on end. I got tired of yo-yo-ing. That’s when I became more engaged in strength training as well, and really embracing the process as much as the results.
Hopefully this gets to at least some of what you wanted to know.