It's easy to beat yourself up and say you should have learned it sooner, but, truthfully, you just weren't ready. And how could you have anyway? You don't tell a newborn to hurry up and learn to use a toilet, for example. That old saying, "To everything there is a season" applies. You can only learn what you are ready to learn when you are ready to learn it. It's developmental and you cannot rush development nor skip steps.
It's also not productive to wallow in guilt or remorse or "should haves". Recognizing how far you come, taking time to reflect on it, is an important part of absorbing the lesson. Another way to look at this is that some people never get there at all. How awesome is it that because you experienced this first hand, you are in a position to help others? Enjoy that well-deserved pat on the back.
Addicted to The Sims since 2000.