I particularly find this very true in my life... I cannot possibly know how to love if I haven't seen and known what it is... and definitely, I cannot extend it to others too.
But rather than relying on human love, which is never perfect, and therefore unpredictable and not the most reliable, there is a Love that is always constant, unchanging and everlasting, unconditional and selfless - unchangeable because it was already nailed into the cross.
What better source can there be?
By Anchored in Christ.