Question to anyone who has been in the Army.

I've been thinking of enlisting in the Australian Army for quite a while now. How will being in the Army effect my girlfriend and any kids we are planing on having later on in life because I wont be around all the time?

To anyone who is in or has been in the Army/Marines/Navy/Special forces or anything along those lines, how hard is it hard to keep in touch with loved ones and how have your family's dealt with it?