There are a few things you can do to tone it down.
1. Mix in some unflavoured VG/PG. You can get the same nic strength as your grape e-liquid so all you're doing is diluting the flavour.
2. Mix in some green apple as
@Letitia mentioned. Green apple seems to tone down everything including...
3. Menthol. Menthol has an analgesic effect, which means it can help to reduce your sensitivity to unpleasant sensations. This is more applicable to harsh nic hit but I imagine it would help with strong flavours too. Try mixing in a *tiny* amount. After a few puffs, the menthol effect should smooth everything out. Be aware though, that menthol introduces another kind of throat/nose hit that some folks hate (I like it).
Good luck quitting. Don't give up.
Ken