"But they who wait upon the Lord shall renew their strength: they shall mount up with wings as eagles; they shall run and not be weary; they shall walk and not faint." Isaiah 40:31

By interpretation, the "they" in this verse is prophetic of the believing people of Israel whose nation will be totally restored to them at the second coming of Christ. By application, this is a promise applicable to all believers who, during their trials, are blessed by God. Patient waiting is a prerequisite to receiving strength from the Lord. We marvel at the ease with which eagles fly on wind currents and warm air up-drafts. However difficult the journey, with God renewing our strength we can "run and not be weary, and walk and not faint." The same God who "keeps us from falling" will keep us from fainting. You don't lose time by waiting upon the Lord.