Hold your breath for as long as you can.
When you feel like taking a breath,
hold on for few more seconds or so.

notice how uncomfortable it feels?

It is the same as when you hold on to something for a long time, always worrying, always looking back, always not letting go.
There is only this much that we as human beings can do, accept and adapt. Only being able to tap at most 5% of our brain, we must learn to deal with what ever we have.

"We cannot change the cards we are dealt, just how we play the hand." - Randy Pausch

I feel that the clenching fist method is not as effective as holding your breath.