It depends on how you practice. I've done retail for about 2 and a half years (not in it anymore) and yeah the horrible interactions weigh on you and are fairly frequent, but there are also others where you can get in depth with things (time permitting) and really make an impact in someone's life. Teaching proper inhaler technique, counselling on their disease states like diabetes management, hypertension, heart failure, etc can be rewarding. If you're in a pharmacy that does some appointment based MTM (I've rotated through a few busy stores that staff people to do this) it's also pretty rewarding and more thorough.
For me though the most rewarding would be where I get to use my knowledge to make treatment decisions and review therapies. But I guess that's subjective.