No it's not.
Don't use a knife, use a surgical razor, or the thinnest blade possible. A 1/100th of a MM in size difference will increase the pain of the cut. If you use a sharp razor, you'll barely feel it.
you'll probably press the razor on your wrist, drag it down, and be immediately shocked at how deep you just sliced yourself open.
But it's ok, pour a warm bath. Light some candles. Getting drunk helps. Slice away, and dip your arms in the water. This will increase your blood flow, and prevent coagulation, making you bleed out faster.
I've dealt with razors so sharp, you don't even notice you cut yourself until you see blood. I personally think cutting is the most over hyped in terms of pain. It would just leave a fuckin mess, and I have a preferred method already, otherwise I would do this.