I think we don't even realise the impact we can have on people, deliberate or otherwise. Years ago, when I finished highschool, this guy came up to me and said "thanks for acting normal to me, it really helped me through the last four years". I kinda knew he got bullied, but I never really realized how much it bothered him or how my interaction with him affected him. He was just this guy, and on occasion I'd talk to him if I saw him in the hallways.

Since then, I've always had the feeling that you don't really have to try hard to have a meaningful impact on other people's lives. Just be nice in general and you'll have more impact than you can imagine.

I shall pass this way but once; any good that I can do or any kindness I can show to any human being; let me do it now. Let me not defer nor neglect it, for I shall not pass this way again.

I don't think that's selfish. When someone dies, it's very normal and healthy to reflect on how we spend our own time, as we're reminded of how precious it is.

Honestly man, other than money that's all we can leave behind. Strive to do your best so that when you leave this world people miss you. That's how you know you did a good job.

Definitely not selfish man. People can only maintain something like 150 relationships at any given time. But if you leave behind something each person you're no longer in contact with can use... Well that makes a real difference for those people, even if it's in a small way.