Was there an "Aha!" moment in your career, when you knew you had made the right decision to serve?

I would say it was at Florida. On Eglin Air Force Base. I just finished a patrol in the worst conditions possible after being depleted for about 3 months. The next morning I went to meet up with the RI with get my ARR. He told me good job and that I don't need to worry about another patrol. Pretty much meaning that I passed. I was in my 3rd month, I recycled mountains, and now I just passed my last patrol. This was only made that much sweeter by standing at victory pond. I had the biggest smile on my face. This was the case because 12 years earlier I was dropped from Ranger school as a 20 year old SPC. It has haunted me ever since. I didn't like that I failed. I just wanted it that much more. But I was able to go back and complete my goal. I still feel that it was my highest point of my career. It wasn't about just getting the tab. It was that even after I failed I never gave up and went back 12 years later while in the National Guard to make things right and I did.

As a very young Enlisted, the first time a small child tugged my BDUs and thanked me for my service, I teared up. It all became clear. I was involved in something tremendous.

((For the record, I still get teary when I get thanked for my service. It never gets old.))

For me, TSgt (Join to see), it was 16JUN73, when I graduated from OCS, and took the oath of office to become a commissioned officer. It had been my goal since I had enlisted, and I was glad to have reached that point.
It was also the first time my parents had attended any of my "graduation" ceremonies. COL Mikel J. Burroughs mentioned that his parents came to his graduation from basic. Mine didn't come then, nor did they come to jump school or any other completion ceremony. However, my family arrived "en masse" (to include extended family) for this ceremony. They watched me raise my right hand and swear the oath before God. My mother and sisters then pinned on my gold bars. It was overwhelmingly gratifying.