There is a saying in the forces that once you are in then you spend the rest of your time preparing for the return to civvi street. If you look at it as a serviceman you are quite well protected from civilian life i.e Council tax, mortgage, having to adjust to a real work environment. You get relitvely inexpensive housing mostly in quite well maintained area's. When you leave the army, your big green safety blanket is taken away from you and a lot of people find it difficult to cope with.
Here's a quick scenario. An Infantry soldier with 22 years in leaves the army, all of a sudden he finds that all his military qualifications and rank mean very little if anything at all. He has to try and find a job that will keep his family with a roof over thier heads and knowing this he will probabally have to take a lower pay rate than he is used to. All the mates he has known for years are now hundreds of miles away, he now has to make new friends in a strange area who have little if anything in common with him.
Thankfully the forces have a good resettlement system that kicks in up to 4 years from your leaving date and good education programs to help servicemen gain civvi qualifications.

Hope this helps

Johno