Just know there is a light at the end of the tunnel. Your children are so helpless and require constant attention and mine woke up hungry basically every 2 hours for almost the first year. You get through it. It helped that my wife took a year off. My kiddo started sleeping through the night at 11 months and that made everything much better. A lot of newborns will do much better and maybe only wake up once per night after a few months. The hard part is also that they can't communicate with you outside crying for like at least 18 months. Once they hit 3 though you should be able to communicate very easily about anything troubling them and that makes life so much more rewarding. My advice is to read to them a LOT and talk to them even more. Do so like they're an actual person and not a child. If you're kid is falling behind in milestones, look and see about early childhood speech therapy. My kid was a good bit behind, but someone working with them helped (probably would've been fine regardless) and they never stop talking now. My in-laws are always confused that I stop and spend time explaining stuff to my kid as they always treat children as things that should obey them without question. It is a little surreal, but parenting method norms have changed a lot in the last 30 years. Reading to them, talking to them, singing to them every night, and doing counting and other activities helps them learn and bond with you.

Know exactly how to get to the hospital when you need to and which have a pediatrician on staff for emergencies.

Start saving for college. Don't worry about fancy clothes as they grow out of everything immediately and nobody cares. Always have spare diapers and sippy cups.