An emotional affair survives on access and secrecy. Ending it means cutting both, not just promising yourself you will feel less.
Start with the channel. The thread, the app, the standing reason to talk — these are the infrastructure of the attachment, and closing them does more than any amount of resolve.
Expect a withdrawal period. The connection was regulating something — loneliness, boredom, the need to feel chosen — and that need does not vanish because the source did. Name what it was carrying.
Decide what honesty the situation requires. Total disclosure is not always safe or wise, but a connection that has to stay hidden to continue is already telling you what it is.
Then rebuild deliberately. Put the attention back into the relationship or the life the affair was quietly competing with, or the fog simply finds a new face to settle on.