People are funny about gifts and favors. They have a strange way sometimes of turning the receipt of one into the expectation of many.
When you do something nice for someone, especially the first time, there’s benefit to mastering the subtle art of putting the gift in its proper context. If you say, “Hey friend, I can give you a ride to work today,” the last thing you want is for them to get out of the car and say “Thanks, same time tomorrow?”
People will often get mad when you can’t (or even just won’t) repeat the gift forever! But me letting you slide on a dollar for your morning coffee one time doesn’t mean coffee is free now.
So it helps to put a little verbal bow on the present. Something like, “Hey friend! The timing doesn’t usually work for me, but I happen to be headed past your place tomorrow morning. Can I give you a ride to work?” It’s still a kind gesture, but you’ve set the stage for it being a one-time event without having to be awkward about it.
The Opportunity Machine 