No soul-friends for me to lean upon. No soul mate to cheer me up. Sometimes the loneliness is unbearable. That will be the right time for me to sorrowfully go to bed while striving to sleep, so tomorrow I& have a fresh new happy day.
If Cas learned this kind of love from Jimmy [powerful family love] it makes sense. And I personally think Dean taught him a different love, unintentional on Dean's part. I mean Cas cared deeply about his angelic family too.
"I am the one who gripped you right and raised you from perdition." he grabbed Dean by his left arm, not the right. Dean knows it's not his Cas -- Into The Mystic promo [gifset] - Castiel, Dean Winchester and the wrong shoulder grab from the promo