Life consists in what a man is thinking of all day.

Whatever occupies your attention is, in practical terms, what your life is made of. Not what you intend, and not what you would list if somebody asked, but what your mind returns to in the gaps: a resentment, a worry, a plan, a person. Add those hours up across years and they are the actual contents.

Spend one day noticing where your attention goes when nothing is demanding it. The answer is usually uncomfortable and highly useful. Then change one input or one habit and watch whether the default subject shifts, because it generally does.