Bad idea to look back.
*Any change, however small, would totally transform the remainder of our lives.
Staying in the military? I cannot tell you how many of my friends stayed in only to quit after 15 years. Had they done the extra five years, they would have had a pension, and yet they could not bring themselves to hang in there. I don’t know all of the details for their decisions. There have been numerous missions that were compromised by people [so-called REMF’s] who just had to commit acts of sabotage by demanding paperwork that was utterly inappropriate, for example, or simply not required … but they insisted. One too many of those will push dedicated patriots out. Years later I would come across documentation of blown missions in which outright treason had been committed.
You just don’t know and can’t know.
Some advice I have heard, which with some thought is helpful: “Bloom where you are planted”.
Perfection is only achievable in the next life.*
The military can be a tough road, yet honorable. I just retired (medical retirement). Praise God, I have a pension that will take care of my family for the rest of my life. I will confess - why did I get out? Jacked up knee and depression. Why depression? I am a former military chaplain who became Catholic. As a chaplain, we were not trained to lead in the tough situations as line officers are. My training and mindset as a chaplain did not prepare me for the situations in which I was involved. I hung in there, but over time my men lost respect for me (they liked me as a person; but a chaplain I was, a chaplain I always will be.)
Can you imagine the chaplain from the old MASH TV series trying to be a line-officer leader?

Well to some degree, that was me.

( I can smile now, it was horrific at the time.)
After messing up my knee in a motorcycle accident and emotionally spiraling downhill from an awful work environment in which I was partly guilty for (certainly not entirely), I ended up in a outpatient mental clinic. My career was fried.
I ended up medically retired with 18 years 10 months. whew… I could have lost everything… God was good…
Should I have left the military when I walked away from the chaplaincy? If I had to do it over, I would say yes, for the sake of those I led, my family and myself. My commanders loved my work as a chaplain and wanted to help me save my 13 year career, at the time.
I have learned a lot about integrity, making tough sound decisions, and how to lead.
Sometimes, God will allow us to be in humiliating situations to make us better people. I think, anyway…