Not everyone is called to do "great things", not everyone can or even should be a great Saint that can be identified from the outside. I like philosophy of Therese of Lusieux who writes about "the little way". That means doing little things with great love. You don't have to be a great hero and save children in Africa. Doing something nice for a work colleague you dislike is just as heroic.
Giving compliments is a loving thing to do, doing small favors for random people (what about letting a lady with only a couple of items in front of you at the supermarket when you have a full basket so she doesn't have to wait?)

You could do one random act of kindness every day or once a week... There's a list of ideas if you search "random act of kindness". Replying people on this site is a service. Donating a small amount to a charity is a nice thing. Do you speak a foreign language? What about offering a free translation to a charity?
Helping your elderly neighbour with something?
When others gossip, why don't you change a topic or walk away?

All of this is a service which challenges you and you don't need to go to the end of the world. You can do this at home and at work.