“What do we live for, if it is not to make life less difficult for each other?” I've used this as inspiration when performing everyday tasks. It gives me a notion of purpose and intention, even though I might be doing something wholly mundane. When I'm washing the dishes, or lifting bags of groceries and arranging them afterwards in the fridge, rather than focus on how boring and detestable these activities are, I concentrate instead on the benefit that I'm doing other people - most notably, my family - by undertaking them. It makes me feel more useful, and seems to intensify the affection that I feel for other people.
After studying ethics I've realized that you just can't create a logical justification for being a good person. It seems to me though, that this is just about as close as you can come. Pain sucks, that's universal. So, lets minimize that. And past the cold rationality, helping people just makes me happy.