When Coffee Is Just A Pretense...

I work at this coffee shop that's like the heart of our town. Everyone thinks I'm all about the caffeine and frothy lattes, but honestly, I just love seeing my regulars' faces every day. But here's a secret... I've been putting extra sugar in one customer's coffee for months now. He's always grumpy when he walks in but somehow turns into this happy-go-lucky guy after his morning cuppa. So yeah, maybe it's not the best thing to do, and yeah, maybe my manager would fire me if she knew... but does anyone think I'm helping him or hurting him? Should I just keep doing what feels right?