Adapting to changing needs

We are very lucky - my daughter could sleep 6 hours straight when she was 2 months old and has been setting new records every month. Her record so far is 12 hours. During the past week, however, she woke up around 1 am several times, and stayed awake for 1 to 2 hours, in fact until we fed her. So last night we fed her more solid food for her dinner, and added some solid before bedtime. And she slept through the night, waking up after 9 hours of sleep this morning. Raising a child is like a game - their needs are always changing and you need to adapt your strategies. It's basically trial and error. The hard part is, when you figure out the right way, you feel guilty for all the errors you have made.