there is a difference

There's a difference between "drifting" and something like, let's say, going seperate ways.

drift (drft)
v. drift·ed, drift·ing, drifts
v.intr.
1. To be carried along by currents of air or water: a balloon drifting eastward; as the wreckage drifted toward shore.
2. To proceed or move unhurriedly and smoothly: drifting among the party guests.
3. To move leisurely or sporadically from place to place, especially without purpose or regular employment: a day laborer, drifting from town to town.

Drifting is slowly parting ways.
It hurts because it is slow.
It hurts because it is slow and painful.
Kind of like a slow and painful death.

And it hurts because once the drift has finally made itself permanent, only then does it sink in. And it sinks your heart down like an anchor.