Answer:
forming a government while the chance exists.
Step-by-step explanation:
Considering the quotation in the question, Thomas Paine in his Common Sense writing, which was published in 1776 when the American colonists were having issues with the British rule, recommended that America should form a government while the chance exists.
This is true because the quoted line says "..it is infinitely wiser and safer to form a constitution of our own in a cool deliberate manner, while we have it in our power than to trust such an interesting event to time and chance..."