You should always pay back people for what you owe.
Rob sometimes forgets to bring his wallet along on the guys' nights out, and one of his friends will always cover his tab.
Rob enjoys those nights out with his friends and wants to keep them going.
Rob is always very careful to pay his friends back within a few days.
Rob has forgotten to pay his friends back many times.
Robs friends laugh when he forgets his wallet, and continue to cover his tab.
Rob's friends  are tired of his behavior and won't allow him to order anything unless he shows he can pay for it.