1. If someone doesn't respect your beliefs, they are not your friend.
This was a difficult one for me to learn, because I thought everyone needed to like me. The truth is there will always be idiots and you don't have to hang around with them. Find people who treat you with respect and be their friend. I had a fellow Marine tell me once that he didn't trust a guy that wouldn't drink with him. He was kicked out in the first year of his enlistment...
2. You don't have to compromise your convictions just because someone intimidates you.
My drill instructors told me to use profanity. Sadly, I caved because I was afraid of going against them. In retrospect, I think I would've gotten a hard time from them if I had refused, but they probably wouldn't have forced the issue. I did learn this lesson later on and when roommates threatened me and mocked me for not going along with their debaucheries, I was able to ignore it. A little immediate humiliation or confrontation is easier to put behind you than the consequences of doing something you believe is wrong.
3. If you stick by the stuff, the people that matter will gain a respect for your moral courage, even if they don't agree with your beliefs.
Eventually, I had peers who would approach me privately and tell me they really respected the fact that I was taking a stand on moral purity, alcohol, tobacco, etc. My superiors poked fun at me occasionally, but I was never held back from being promoted because I was "different". If anything, the fact that I didn't get stupid drunk probably helped me move into leadership.
4. The confidence you gain after not compromising your belief system is invaluable.
I feel as if I have moral courage that I never had before this experience. My stand against alcohol is much stronger now because I've seen the effect it has on otherwise good people, and I am able to say "no" under extremely difficult situations. Until you've experienced such strong opposition, you can only hope that you will respond the way you ideally would like to. Now I know how act under pressure...
5. Experiencing public ridicule makes you a more humble person.
Learning how to let a painful comment "roll off your back" when you've been ridiculed in front of 100 people is very hard, but gets easier with experience.
6. Loneliness isn't all bad.
When everyone else was at the strip club, bar, or dance club, there were many nights I stayed in my barracks alone. I was very tempted to go with them and justify it by calling myself a "designated driver", but in my heart of hearts I knew this would violate my conscience. Usually when I took a stand, I found myself standing alone. It takes getting used to, but it's better than getting dragged into the filth that everyone else is wallowing in.
7. Anytime you go against the flow, you make enemies. This can't be avoided.
Someone once put a pornographic calendar up in our berthing on ship. I took it down. The entire platoon got angry with me and demanded I put it up. Officially, the rules on ship are that pornography is not allowed (this is NOT enforced) so I knew if push came to shove I had the law on my side. I told them if they wanted it, someone could put it in their private rack (which is covered by a curtain) but it wouldn't hang in a public place. I was public enemy number one for a couple of days. Oh well...
8. You have to be proud of a clean life, not ashamed of "lack of experience".
Someone once told me I should sleep around because experience is the best thing to bring into a marriage. THIS IS A LIE!!! My wife and I have an extremely close, happy marriage which is enhanced by the fact that neither one of us have been with anyone else intimately. Don't fall into this trap, because it leads to discontentment. A fellow Marine used to call me "Darth Virgin" in an effort to embarrass me. I learned to be proud that I could still bear the title of a virgin.
9. Conformity gains you respect among peers, but non-conformity (the kind I'm talking about) gains you respect among superiors.
Many (not all) of my superiors recognized that I was different than the rest of the crowd, wasn't afraid of opposition, and that this quality would make me a better leader. Someone who yields to pressure from peers will never be able to make the right decision when it's not the popular one.
10. You become like who you hang around.
I made it a point to spend as much time as I could with those who believed the same as me. I had a friend who was a Christian, but at liberty ports he would run with the wrong crowd, get drunk, and end up cheating on his wife every time. He was always so ashamed of his conduct afterward and would ask if he could spend liberty with me next time so he would have some accountability. Sadly, the temptation always got the best of him and he couldn't leave his old friends. If you have the choice, spend time with those who lift you up, not those who drag you down.