I have 3 children. My first two are 15 months apart, and my middle and last are 16 months apart!
Oh R., I remember finding out that I was pregnant with our second child when my daughter (our first) was only 5 months old! Yeah, I cried and felt that I wasn't going to be able to breathe and wondered how I was going to ever be able to handle two children that were going to be 15 months apart! Once you calm down and remember that God never gives you anything more than you can handle you can do fine.
My biggest advice for you right now is:
1) Get your oldest on a schedule. This will help you be able to fit the other into the already existing schedule.
2) Find a form of discipline that works for your family NOW. If you have established discipline then on those days when you have no patience it will be much easier.
3) Make your oldest child a big part of everything regarding the baby. My kids went with me to every appointment and even saw the ultrasound.
Personally I love having the kids so close in age. After our beautiful little accident Rocco Mario, came along and I had settled through the craziness of the first 3 months I told my husband that if we were going for a 3rd child then we needed to do it before Rocco Mario was one. Well, I now have Tino Giovanni how is 10 months old, the boys are 16 months apart. I think they get along really well, there isn't a lot of fighting or jealousy in our house. Ofcourse I'm big on teaching them about sharing, being under control, loving one another, and other bibical principals which I think helps a lot. I also make sure that they know to use their words and not hands (which was hard for the little ones who don't talk or just started talking, but the older one has this mastered).
I think that as long as you breathe, try to relax and just enjoy the fact that they are so close and will be great friends and always have a companion, you will be just fine. It really was only about the first 3 months that were hard. I had major guilt regarding leaving my first sometimes while I was nursing and putting the baby down. Once I overcame the fact that I couldn't devote my attention to my oldest all the time, it wasn't that hard. Honestly, I think that I had a bigger adjustment to them being so close and adding another child then they did any of the time!
Good luck and if you need anything, feel free to email me ____@____.com or call me ###-###-####). You can do it! I wouldn't have it any other way, and I had thought of having them 3 years apart....now I look at people who have them 3 years or more apart and think that they are the crazy ones and not me! LOL
Oh, and another thing, be prepared to hear everyone say, "Oh, you have your hands full don't you?!" My response is, "Yes, Full of love!"