"And now here is my secret, a very simple secret:
It is only with the heart that one can see rightly; what is essential is invisible to the eye."
By faith, and not by sight.
All the keys to life are held in the things which are not visible to the human eye: love, happiness, companionship, purpose, hope, joy...none of these things can be seen. They are, instead, felt by the heart and understood by the mind. A life that lacks what the heart needs is a one where it's difficult to see a future and missing the feeling of fulfillment. Your heart will always point you towards the correct path. It seeks the things that our eyes do not: our eyes look for lust and not love, it finds material happiness and companionship by the quantities, not the qualities; our eyes direct us towards worldly purpose and not a greater mental and spiritual purpose; it is blind to what hope and joy are because those are things that cannot be physically identified or materially attained. When we navigate the path before us, we are guided by the compass of our heart -- we walk by faith, and not by sight.