Planning invites calamity. To stick to the plan requires the abortion of Now in the name of a non-existent future.
The common line is that planning is our human everything - the bread and butter of life. That planning is a safeguard. That planning encapsulates all that is able to be affected by our daily life, our decisions, our dreams.
But, the one constant that runs through and around and beneath them all is change. It erodes the very foundation of immortality, of memory, of nostalgia and hope. Change creates and destroys at devilish speeds. It niggles into our emotions and impulses. Change is impersonal, and impervious. Change is all.
Disposing of thoughts fore and after awakens you to the thrilling danger of Now. It allows for immediate absorption of the joy of living. Investigating existence as it is means stepping through a doorway often shut by pangs for safety and satiation - desires like sink holes that will never be filled for long. Adaptation holds the only key to happiness.
The only caveat being, happiness is not forever.