R. Yehoshua b. Karcha says: An analogy: A king gives a feast and invites guests. His loved one is sitting among them and he tells him to take a choice portion; but he (the guest) lacks the power to discriminate. Seeing that this is so, the king takes his hand and places it on the choice portion. This is the intent of (Psalms 11:5-6) "The L-rd is my portion and my cup.
You hold my lot. The choicest lot has fallen to me. My inheritance, too, is beauteous to me." Some are given their portion but are not happy with it.
But Israel rejoice and glory (in their portion). For there is no portion as choice as theirs and no heritage like theirs and no lot like theirs. And they acknowledge this and praise (the L-rd) for it, viz. "The choicest lot has fallen to me. I shall bless the L-rd who has counseled me."