Don't double it next day if you miss one, just ignore the missed day. It's not like missing a contraceptive pill, not even if you still bleed.
Try not to miss doses esp early on in taking T - that is the advice I've been given by the GIC - as if you're erratic with it over several weeks you may disrupt voice drop etc. If your pharmacy isn't reliable (like mine) try to keep back a reserve supply. I keep back a minimum of a month's worth, just in case. 3 months, usually.