A closed door is kinder than one you keep half open just to slam later.

Leaving something half ended is usually more painful for everyone than ending it. Ambiguity keeps hope alive on the other side and keeps you managing a situation you have already decided about, and the eventual close tends to be harsher for all the delay. Clarity early is the gentler option even when it does not feel that way.

If you already know your answer, say it plainly and soon, without a list of reasons. Keep it short and do not soften it into a maybe. A clean ending gives both of you somewhere to go.