You can do more than you might think, because the world is round. Every action you make is like a never ending chain, touching EVERYTHING within reach of that thing. You don't even realize it, but with one smile you might of passively reached at least 100-1000 people by chain reaction. That's how negativity, and positivity travel the world.

I'll explain it even more: Say you're in college, and you walk into your first class. Something happens, because of someone, and you get angry. People around you notice your bad mood, and they pick up on it right? Well, then those people go onto their daily activities, bringing their bad moods to other people, and the people they influenced do the same to more people. Your behavior ALWAYS matters. It's not futile.