live today

गते शोको न कर्तव्यो भविष्यम् नैव चिन्तयेत्।
वर्तमानेन कालेन वर्त्तयन्ति विचक्षणाः॥
चIणक्यनीति
gate śoko na kartavyo bhaviṣyam naiva cintayet|
vartmānena kālena varttayanti vicakṣaṇāḥ||
caṇakyanīti

ഗതേ ശോകോ ന കര്തവ്യോ ഭവിഷ്യം നൈവ ചിന്തയേത്
വര്തമാനെന കാലേന വര്തയന്തി വിചക്ഷണ):

do not grieve over what has already happened, and do not worry over what is going to happen.
The learned and brave men live up to the present situation with utmost ability and sincerity.
Every lifestyle consultant or author has uses this dictum to encourage people to live their life full.
Dale Carnegie asked us to live "in day tight compartments"
Someone said, "tomorrow, do thy worst, for I have lived today"
 Shelley wrote 
"We look before and after,
And pine for what is not:
Our sincerest laughter
With some pain is fraught;
Our sweetest songs are those that tell of saddest thought."

The advice by the master Chanakya and other greats should not lead us to hedonism.  We should be always conscious of the path we have trodden in reaching the present state. Moreover we should have a clear-cut action plan for the future.  But while performing today's duties we should not be bogged down by our past and future.