It's not easy when you try to do a good thing.
Kept a little puppy for about 2 weeks in my house, with my cat, and finally ended up having to take her to a shelter.
I'll tell you this story though....... Little kid is walking along the beach and picking up these starfish that have washed ashore, tossing them back into the water. The starfish on the shore go on for as far as the eye can see. Suddenly, an old man walks up to the little kid and asks what's going on. The kid replies, "Saving these starfish." The old man looks puzzled and answers, "You can't save them all. Look how many there are!" The little kid, undeterred, picks up another starfish and chucks it into the water, then says "Saved that one," with a smile.
Moral of the story, you can't save them all. You can definitely save some though and that's already what you're doing.