The Eternal Present
Only the present moment is real; past and future are mental constructs. Virtue can only be practiced now.
Marcus Aurelius described time as a river of vanishing moments. The past is gone; the future is not yet. Only the present instant is real, and only the present is the arena of virtue and action. This insight redirects attention from regret and anxiety to active engagement with what is actually happening.
Do not squander time, for that is the stuff life is made of.
Stoic present-focus parallels Buddhist mindfulness, Zen immediacy, and modern 'flow' as states of complete engagement with the actual moment.
Epistulae Morales