They are an absolute pain in every way, for a couple of days every couple of months my fingers are sore and bruised from doing this.
I can only advise,
Make sure you are hydrated
Make sure the room and you are warm, possibly after a shower.
Take a brisk walk or dash up and down the stairs a few times just to get the blood pumping a tiny bit faster before you begin
Relax and make sure you keep your hand lower than your heart, I would recommend setting everything up so you can be stood up to do this.
Good luck 👍