It is not selfish to have needs (everyone has them). They must be fulfilled (or you aren't okay). When we lose someone, we have more needs (I've experienced it [people helped me]).
I need to help people [want and need (need to)]. It's part of who I am (what makes me happy). Waitressing most days a week helps fulfill it (physical help [not emotionally helping them]). You're not being selfish (if it's me [it's okay if you are]). You're helping me too (letting me help you).