My 2 DDs were 15 months apart, the first year after DD2 was born was a complete nightmare (sorry). But having said that, they are now nearly 5 and 3 1/2 and both seem fairly ok, and I still have most of my sanity left....
Agree with the other posters, invite other kids over, go to others houses, Cbeebies, soft play was always a good break if you have a nice one near you.
Alternatively do what I did, practically hurl DC2 at DH as he comes through the door from work an lock yourself in your bedroom for an hour to recouperate