I can really connect with you on that one, I have a friend who struggles to and she sad the same thing that she doesn’t feel like she makes a difference especially with what’s happening. I pointed out that she answered her phone last week… it made a difference to me. It made that very dark place a little lighter and she has said that I do the same when I agree to meet her. I do have quite a lot of support around me, I suppose I become blind to it at times 
And it’s so awesome you made someone feel so good, I always find making someone happy makes me happy too and making a difference to someones day is the best feeling ever, even if it’s only little.