I've never used those 2 words together that's all. And I'm guessing you are using it as a metaphor. But for what?
Yes, it's a metaphor. Childhood is typically a time of "ignorant bliss" and I sometimes do miss it, and wish I could visit it again. As we grow and mature we start to realize and also shoulder the harder truths and responsibilities of life. Which brings more "sorrow" because of seeing things more as they really are, as we discard the pleasant illusions and rosier coloured glasses of childhood.
Heb 5:11-14
Of whom we have many things to say, and hard to be uttered, seeing ye are dull of hearing.
For when for the time ye ought to be teachers, ye have need that one teach you again which be the first principles of the oracles of God; and are become such as have need of milk, and not of strong meat.
For every one that useth milk is unskilful in the word of righteousness: for he is a babe.
But strong meat belongeth to them that are of full age, even those who by reason of use have their senses exercised to discern both good and evil.
So how do you see this scripture? I see the milk as being all the positive things and wonderful promises of scripture....they are so easy to take, all sunshine and roses so to speak. But the meat of the word are the things in the word that are harder to take and digest, but they are necessary if we are to grow stronger and mature. In places the milk and the meat may seem contradictory but that is only if we aren't rightly dividing the word of truth.
Little babies and toddlers know nothing of the dangers and vulnerabilities of life, and they typically see their Dad as a jovial funny guy who is a lot of fun to be with. They know nothing yet of the dangers, toils and snares that lurk outside the playpen...and they have not yet experienced their Father's discipline, nor do they know that Dad runs a big business and has the power/authority to both hire as well as fire who He wishes. More than that of course, He is a Great King who has power of life and death.
The bible says to whom does He teach wisdom and understanding....to them who are weaned from the milk.....and Solomon wrote that with more wisdom comes more sorrow. Anyone who is an adult knows that adults are not as carefree and happy-go-lucky as we typically were when we were children. No, we are more serious and care-ful, and wiser to the under-belly of life in this world.