You'll do fine
Motherhood can be scary. Whether you were a CEO or a waitress before giving birth, you will never have done anything carrying quite the same importance before having a baby. Parenting is a huge responsibility, and often mothers will take on most duties especially in the early years. You may feel that you need advice from your own parents, relatives, friends, books, doctors, magazines and blogs. Here's the secret: in most cases, your common sense and maternal instincts will lead you to make the right decision just fine, without anybody's input. You will also know when you truly need help, medical or otherwise. Moral and psychological dilemmas may come later, but caring for a young baby is mostly instinct. Feel free to tell people to go away when they offer unsolicited advice, or to apply the "in one ear, out the other" tactic. You'll do fine. All by yourself.
You'll find nothing disgusting anymore
You will see most of it during pregnancy and birth, anyway: urine, feces, vomit, blood... When your baby is born, you will take things to a whole new level. You suddenly like to analyze your baby's bowel movements (See: Is your infant's poop normal?), will think nothing of cleaning your baby's face with spit, and won't mind discussing your postpartum genitals with your OBGYN either. Later on, you'll tell your kid stuff like, "How many times do I have to tell you this? It's Batman, not Buttman! If you say that again, I'll send you to time-out!" (Only to be told, "look mom, I drew Buttman. Poop comes out of his mouth when he talks.") Toddlers and preschoolers can get quite obsessed with bodily functions. In the meantime, we'll leave the fascination with you the new mom.
Breastfeeding is normal and natural. Despite what most people say, it doesn't have to hurt, or be gross, or give you mastitis. Breastfeeding burns calories and helps you lose weight more quickly. It is free. It is just about the healthiest thing out there it can protect your baby from diseases and even cure conjunctivitis Breast milk always comes with you, and can always be served at the right temperature. I just had to mention this one, since so many women say that breastfeeding hurts, and sucks. It really doesn't have to.
You may still look pregnant after having a baby
Some moms actually get questions asking them when they are due. Most moms still look slightly pregnant after giving birth. You may be able to squeeze into your old, pre-pregnancy clothes right after you have had a baby, but they will just not look the same. You can work on weight loss after pregnancy through exercises (especially abdominal!) and the right diet. Some changes just may turn out to be permanent, like stretch marks or saggy breasts. And the chances are, you won't even care about that.
Parenting is controversial
Whatever you do, a whole army of people will be waiting to criticize you. Motherhood and fatherhood are much more controversial than politics and religion combined, or at least it will feel like it while you are in the thick of it. Random strangers will ask you if you breastfeed, and your mother in law or other relatives will have a go at you for circumsizing your baby boy, or not doing that. Friends will ask you if your baby sleeps through the night yet, and elderly neighbors will make negative comments about the clothes your baby is wearing. Are you sensitive about these kinds of idiotic comments? Don't even think about visiting internet discussion boards for new moms, or reading mom blogs. While anyone can be military about parenting, other moms are definitely the worst.
Parenting is the greatest thing ever
Parenting is more challenging than any job you have ever done, though not every mom finds every stage a challenge. Don't think you are going to have a smooth ride all the way if your baby is easy to look after at the moment. The dilemmas increase with age, but so does the fun. Kids are not going to live up to your expectations, but they will blow your mind and make your heart explode with love. Enjoy the ride!