Human being wishes or thinks about what he ought to be rather than accepting himself as he is at the present moment.
He either analyzes the past happenings or worries about the future. By doing so he ruins the pleasure of the present moment.
Enjoying the present emphasizes complete awareness of our activities from moment to moment like work while work and play while play, other than mixtures.
While performing any activity, thinking issues not concerning it might spoil the pleasure of the same.