Infants aren't easy in RL, either. Most of it simply requires the player to sit back, relax a bit and just tend to the wee one's needs as you would other Sims. I play on autonomous and for the most part my Infants have managed to fulfill many milestones, and some of them entirely on their own. My first go around, I did find myself stressed out, so I completely get where you're coming from. After a bit of self-talk, however, (where I decided to just relax over it) things started to go better for me. If you allow yourself to not make everything perfect (I am a perfectionist to the enth-degree), then you may find it's not so bad. By the time I hit the second kid (in my Sims' family) which were twins! I found myself having a ton of fun, believe it or not.
Just keep them alive and in your household. That's the overall goal. And have FUN.
