This quote is often attributed to Theodore (Teddy) Roosevelt. However, in his autobiography, he credits it to Squire Bill Widener, stating that the quote sums up one’s duty in life. In a very succinct way, it does sum up one’s duty in life. In life, the most you can ever do is what you can do. Doing your best is the primary target. Meanwhile, you make the best of what you have at any given moment wherever you find yourself.
Further Reading: “The best preparation for tomorrow is doing your best today.”