Dear New Mom,
You are probably getting advice from all sides - maybe to much. You have seen the lists online of what you should know, you're friends are all chiming in, and of course there are the baby books. You probably don't want one more message, but I can't help myself, because I think it's an important one.
My advice for new moms:
Don't take it personally.
That's it. Simple, right? You are probably wondering what on earth I mean. I mean that your baby's (or toddler's) habits are not a reflection on your parenting. I am sure there is some age when this begins to change, but I think it is always true to some extent.
Your baby may be a poor sleeper, or have separation anxiety, or refuse to take a bottle, or be grumpy, or have a health problem. Your toddler might be a picky eater, or throw tantrums, or get ear infections, or bite his classmates, or need speech therapy, or be slow to walk.
If they do, it's not your fault. You did not do this to them (and no, they are not trying to punish you). There isn't a magic thing you should have done or a parenting technique you could have used. Don't beat yourself up if your kid isn't perfect. No adult is perfect, so why do we count it as personal parenting failures when a baby or toddler isn't?
Being a good parent doesn't mean having a perfect child, it means loving your child and helping them to get through whatever challenges they face (whatever challenges they drag you through). Don't add a degree of difficulty by believing those challenges are your fault.