Honestly, this.
If need was the only driver, I'd be in a bad way - I can't save everyone even if I had limitless time and resources. It is a bigger problem than I can tackle as an individual and stay healthy. All I can do there is support institutions that try.
But that person in front of me right now that needs a boost? That small goal is in my grasp, and I need to live with myself. I can't always help, but I try to help enough.