Well, I think I'm still going through that process, but ...
As a kid and teenager I really didn't think about diabetes much. I was responsible with my shots and diet, and my A1c stayed around the low 7% range (not bad on two shots a day).
Then as a late teenager/early young adult I slacked off on control as is usually common. I still did my shots but only tested 2-3x per day (which was actually not horrible considering 4x is what was recommended) and didn't really care what I ate, didn't do any exercise at all. My A1c rose into the high 8%/low 9% range where it stayed for about five or six years.
Then in my mid-20s I suddenly got interested in diabetes and read a bunch of autobiographies. Every single autobiography had the person developing complications at some point. I realized that at 25 I had already had diabetes for over 15 years, and that I was going to have to live with this forever and didn't want complications. I decided I needed to do something about my level of control.
I switched to MDI and then the pump, started testing 10x a day, learned about diabetes (I had literally forgotten everything, I didn't get much education when I was diagnosed as I was young), started exercising regularly, started logging everything. I brought my A1c down into the low 7% range again. Even got a few results in the high 6% range!
About two years ago I went through MAJOR burnout. We're talking not counting carbohydrates, not logging, sometimes not bolusing for food at all ... A1c rose into the mid-8% range.
Decided after about six months to a year that I was being super unhealthy and had to snap out of it. Lowered the amount of carbohydrates I ate, exercised daily, started logging everything, and got my A1c back into the mid-7% range. This is where I am today and have been for the past year.
My ultimate goal is to get my A1c to around 6.5% or below and keep it there, but it's also trying (and failing) to reach this goal for five years that led to my major burnout. I don't want that to happen again, so am trying not to stress out about it. I have, however, made MAJOR changes in the past six months, so I'm hoping this will help me break into the low 6% range (where, in 20+ years now, I've never been).
I think years down the road I might look back and see the past eight or so years as my "turning point" interrupted by about a year of total burnout.