How on Earth do you know what to do out of the myriad possible actions until you have substantially thought out what you should do? There are many, many values one can act to attain, achieve, and create. One must think about which to pursue and how to pursue them. Then one must think about how to maintain them and how to use them to achieve one's happiness. There is little point in blind action.
It is true that when acting to attain one value, one puts oneself in a position to learn about more things and to make wiser decisions in the future. There is a very critical feedback from a proper combination of thought and action. And having thought about which values to pursue and how to attain those values, the follow-on action is required. Yet it all starts with thinking and it is much better if that thinking is rational, if one is to actually be successful in attaining the values one sets out to attain.