I’m a relatively new trainer myself, and although I can’t offer much advice, I can tell you that one of the biggest things for my clients so far has been an emphasis on enjoying fitness. I’ve found that if you can get someone to have fun doing something active, then you’ve already won half the battle. As long as you are designing safe, effective, and fun programs that are keeping your clients coming back for more, then I think you’ll be ok. That’s my experience with it, anyway.
I hope you have great personal training experiences! (I won’t say good luck because luck implies lack of ability.) =)