On the road to health, wellness, and happiness we can easily get caught up in a confusing numbers game. We track calories, measure our heart rate, weigh our food, etc. This becomes a problem when we over-analyze or fall into stagnation. On the one hand we become overly neurotic, on the other hand we stagnate by never experimenting with ourselves.
CrossFit gives you a different, easier metric: power output. Looking at how much total work you are doing over a certain period of time will easily tell you how well you performed. The when you race that clock and see your times getting better you can easily see if performance is going up. When we take care of performance, all the other things (weight, strength, capacity) will fall into place.