“It was, of course, another test. Everything in human life was a test. That was why they all looked so stressed out.”

Source: I Shall Wear Midnight

The Soul of a Butterfly, 2004
Variant: All through my life I have been tested. My will has been tested, my courage has been tested, my strength has been tested. Now my patience and endurance are being tested.
Source: The Soul of a Butterfly: Reflections on Life's Journey

Source: The Winner Stands Alone

Source: https://play.google.com/store/books/details?id=LXlhDwAAQBAJ

Source: Faith vs. Fact (2015), p. 34

Source: The Purpose Driven Life: What on Earth Am I Here for?

Letter Seven (14 May 1904)
Letters to a Young Poet (1934)
Variant: For one human being to love another human being: that is perhaps the most difficult task that has been given to us, the ultimate, the final problem and proof, the work for which all other work is merely preparation.
Source: The Selected Poetry of Rainer Maria Rilke
Context: People have (with the help of conventions) oriented all their solutions toward the easy and toward the easiest side of the easy; but it is clear that we must hold to what is difficult; everything alive holds to it, everything in Nature grows and defends itself in its own way and is characteristically and spontaneously itself, seeks at all costs to be so and against all opposition. We know little, but that we must hold to what is difficult is a certainty that will not forsake us; it is good to be solitary, for solitude is difficult; that something is difficult must be a reason the more for us to do it.
To love is good, too: love being difficult. For one human being to love another: that is perhaps the most difficult of all our tasks, the ultimate, the last test and proof, the work for which all other work is but preparation.

Source: A Path with Heart: A Guide Through the Perils and Promises of Spiritual Life