A life of action and a life of reflection are both part of a thoughtful existence. We need action to form the basis of our reflections, and reflections to form the basis of our actions. Experiencing life deeply means to be aware of the importance of both action and reflection, and the interaction between the two.
If you have some familiarity with the writings of René Descartes, you will know that he believed that thought is the basis of existence. But what is thought? In attempting to experience life deeply myself, I am often puzzled by the behaviour of other people. I am especially perplexed when observing those whose actions frequently make me conclude that they do not think very deeply at all.