When I got back to running after I had my son, I started with shorter distances and walked a lot. You'll be surprised how quickly you get back into it, but don't worry about how slow you are, that can get depressing. Just concentrate on either time or distance (say running 3 miles, or running for 30 minutes).
I think it's more mentally hard to come back after being laid off. You feel like you should be running more/faster. Give yourself at LEAST the amount of time you were off to get back up to par. If you've been off for a month, it'll probably take you about a month to regain that fitness (give or take). And just remember that you run because you LOVE IT!
Patience and Fortitude - Mom
There ain't a thing I've faced that's been too much for me - Classified "Inner Ninja"