I would like to express some ideas, but I can't make sure they are proper expressions. Please see these sentences:

When you know your family will add a new member, you are sure of one thing: you are determined to do everything in your power to give your new family member the best possible start in life.
Nature has equipped human beings with an instinct to protect and nurture infants but has not provided us with universal rules for parenting. What can you do? You can stimulate your children's curiosity and imagination; you can help them learn to overcome frustrations and evolve strategies for solving problems and reaching goals, to experience problems as "challenges" that can be met, not merely as "stress" that they cannot cope with. You can encourage your children to develop language abilities that will help them to learn more about their world and communicate with others. You can help them understand that their actions-or nonactions-have consequences. You can help them build rational thinking. You can strengthen their sense of accomplishment and build up their sense of responsibility. Adults can raise a child's self-esteem by making him or her feel a part of "us" and not just an isolated "me."

Are they proper expressions? Thanks!

Best regards.
Yup. The clause from "you can help..." to "...with" is a little long and easy to get lost in, and it's mildly inconsistent to join this to preceding clause with a semicolon, but to the following clause with a period. There should also be no hyphen between "nonactions" and "have".

I would change "you are sure of one thing:" to "you can be sure of one thing: that".

But they are all proper expressions.
Thanks for your reply, I'm going to take your advice.

Good luck.