Congratulations!
Its fine. Physically hard work (especially if DC1 isn't walking), but there are huge benefits.
Such as - you have two babies, which means they do the same thing at the same time near enough. One lot of teething instead of two, that kind of thing.
You don't get used to a full nights sleep, so you won't miss it.
If you are physically fit, and have had an exercise routine of sorts, stick to it. Fitness and stamina will help hugely.
After about two years you reap the benefits. My boys are 14 months apart, are very close, both like the same things and share friends. The fight and I referee, sometimes constantly, but they have companionship and comfort from one another.
I didn't realise how hard it was until I looked back on it. At the time I just did it and got through it. But I found going from 1 child to 2 hard, not the age gap as such.
I felt terribly guilty for DS1, as I realised he was still a baby, but compared to the newborn, he was MASSIVE. He went from baby to toddler in an instant. I really beat myself up, and felt terribly guilty about it. I also felt guilty for the new baby, as I was trying to over-compensate for DC1. In reality, I should have just cuddled up on the sofa with my two babies and not tried so hard.
Now I have 2 more DCs, so have 4 6 and under. I could go on about how great it is having them close together, but I've gone on quite long enough and have probably bored you to sleep