The most common answer I have had when I initially start asking people this question is "nothing". If the insight that we become what we think about most of the time is true then thinking of "nothing" leads to nothing.
Much of our thinking is habitual. Changing habits is not easy. It can be simple, but very rarely have I known it to be easy. Asking yourself this question from the turn of the last century has the potential to reveal what you tend to dwell on most of the time.
Quite often I would find myself reenacting a situation I had seen, read about or even just imagined and would put myself in a positive pivotal role in the story. Now if you are a psychologist, that probably tells you more about me than I would care to know! For me, it revealed I was not as intentional with my mind as I imagined I was.
A great exercise is to find someone you trust and remind each other that "you become what you think about most of the time". Repeat this back and forth between yourselves a couple of times a day and then at random intervals ask each other "what are you thinking about?".
A fun repartee can then ensue where you are reminded that we become what we think about most of the time - and if we are thinking about nothing, then our days are likely to pass us by without anything deliberate or intentional happening. Your mind is a muscle, and much like your physical muscles, it can and should be exercised.
If you accept the challenge to ask yourself several times through the day "what am I thinking about right now?" (it can be useful to put an alarm on your phone to prompt this) I encourage you to have a small notebook and merely record your thoughts.
My guess is you'll be amazed at how often your thinking is automatic, undirected and highly likely even negative. Knowing this then allows you to take more responsibility for your thoughts and through that your actions. Remember it is your mind and you have the ability ("response-ability") to choose your responses and direct your thoughts.
Decide who you want to be. Start being that person every day and that is who you will become.
Mike Clark is director and lead trainer and facilitator at Think Right business training company.