like jay said...it depends what you're injecting. if its fast acting stuff, and you missed 7 days, you could pick right back up again. or, if you know you'll be away for a while, just start PCT.
if using longer acting esters like enanthate or deca or
EQ, again, you could just get right back to it, or go into PCT. if you know you'll be away for a week, and you know this ahead of time, you could double the dose the week before you leave. even though your blood levels will fluctuate, i'd rather have them fluctuate up rather than down.
if however you're being deployed, or wont be able to get back to it for a longer period of time, then i'd forget about the cycle and hit the clomids.
have a nice day