Dude,
I know the feeling of wondering if you did the right thing. Here is my story, if you feel like reading it! (not trying to threadjack, just trying to parallel your situation)
I went on a double boat dive with my girlfriend who hadn't dived in over a year. It was our 6th or so dive and our first ever non-divemaster led dive.
I had ALL new gear, bought a few days earlier - head to toe.
It was also my first boat dive ever. I hadn't eaten yet that day either (stupid). It was cold, choppy and to top it off, it was a 25m dive - deeper than any dive either of us had done to date.
Conclusion: The dive majorly sucked. I was worried about my girlfriend the whole time, clumsy as hell due to new gear, sea-sick and breathing heavily. I also had trouble equalizing my ears. It was just generally a SH*TTY dive, so I gave the thumbs up with 1500psi left and decided that was it for the day. Since I was so anxious to get out of the water, I wasn't thinking straight and I neglected to do a safety stop. I ended up worried about DCS for the next 2 days and called D.A.N. just to feel better.
Basically we threw 120 bucks in the toilet because we didnt do the second dive of the day, and we embarassed ourselves because everyone else on the boat had a great time. The boat operators kept trying to get us in the water for the second dive, but we said fuggedaboutit.
In the end, I don't regret our decision at all. I've been diving a lot since - all hassle-free dives, more advanced than the one that overwhelmed me. My confidence is totally back and I don't even care about the money I lost. In an equipment intensive hobby where you're likely to spend TENS OF THOUSANDS over a career, what's 100 bucks in the long run? NOTHING, unless you kick the bucket trying to save those dollars.
There will always be another chance to dive if you don't lie to yourself about your capabilities, or let your friends lie to themselves about theirs.