Today's blessings, tomorrow's strength

What if my present blessings do not last?  What if today turns out to be the very zenith of my blessings; that life gets, and stays, harder starting tomorrow?  Would I enjoy today less if I knew that?  Would fear of the future make me less grateful for my present blessings?  Would I not strive to use my present blessings, and gratitude for them, to grow and to increase my capacity to bear travail?