Little things count, because they add up to big things. I'm thinking of positive things, however. A kind word, a gracious gesture, doing something unexpectedly kind, no matter how small...these are the nails that hold together a strong relationship between two people.
On the other hand, promises broken, no matter how small, snide comments, refusing to budge on issues, petty jealousies...these are the termites that eat away and will eventually erode a relationship.
I've found that in the long run, the huge things are rarely what make or break a relationship...it is the little things that count the most.