felicitous
Perfectly suited to a situation and making it happier.
Felicitous means well-suited to the situation, expressed in just the right way, or producing a happy result. When you choose felicitous words, you've found exactly the right ones for the moment. When a solution is felicitous, it fits the problem perfectly.
Think about giving a speech at your grandmother's birthday party. You could say many true things about her, but a felicitous remark might be telling everyone about the time she taught you to bake her famous cookies. That story feels just right: it's warm, personal, and makes everyone smile. A less felicitous choice might be mentioning something embarrassing or bringing up a sad memory.
A teacher makes a felicitous comment when she praises a struggling student in exactly the way that builds confidence. A compromise is felicitous when it solves a problem and leaves everyone satisfied.
The opposite is infelicitous: awkward, poorly timed, or making things worse. Learning to be felicitous, to choose the right words and actions for each situation, is one mark of growing wisdom.