A good motivation is what is needed: compassion without dogmatism, without complicated philosophy; just understanding that others are human brothers and sisters and respecting their human rights and dignities. That we humans can help each other is one of our unique human capacities.
When something needs to be done in the world to rectify the wrongs, if one is really concerned with benefiting others, one needs to be engaged, involved. This is action out of compassion.
Half of the harm that is done in this world is due to people who want to feel important. They don't mean to do harm. But the harm does not interest them.
Keep away from people who try to belittle your ambitions. Small people always do that, but the really great make you feel that you, too, can become great.