It isn't super dangerous to discontinue an SSRI without a doctor's supervision. That's the way most people do it. And many doctors still refuse to admit that there can be withdrawal problems andeither tell people they can just stop taking them or they spread discontinuation over two weeks.
Abrupt discontinuation can cause nausea, dizziness, headaches as well as mood swings unrelated to the reason the drug was prescribed. The physical symptoms, if they occur, can last two weeks or so, though the headaches from Effexor and Paxil can go on indefinitely The psychiatric symptoms can last longer.
That said, I would never advise anyone to abruptly discontinue an SSRI/SNRI antidepressant (Effexor, Cymbalta), particular from high doses. I've heard too many true horror stories.