Take Care...

It occured to me the other day about the phrase "Take care of yourself".
What is meant when we say it, and is that what we are actually saying? You never say 'Take care of yourself' to a child. At least I never have. You almost always say the phrase in parting for an extented period of time. Sometimes it is said to friends, but mostly to people to which you're not that close to.
Which then leaves me to wonder if it is a resignation of sorts. Are you really saying 'I can/will no longer take care of you, so you must do it alone' ? Or are you hoping and in your head somewhere disbelieving that they are capable of taking care of themselves without your assistance.
That particular thought strikes me as arrogant, but how often is it true? It could be a mental thought of 'Dear Goddess - What on EARTH will they do? How will they manage without me in their life to straighten up for them.'
Or could it just be that in this, a time when everyone is Dog Eat Dog and looking out for number one, that the speaker of the phrase is stating the obvious in a sugar-coated way. Are they saying, 'I have no interest in your life anymore as it fails to amuse me' or alternatively 'it is far to much effort to maintain an interest in you for the amusement that I get'
What are we really saying when we say 'Take care of yourself'? Is it the nice/sweet thing to say as you watch someone you've invested your time in leave? Or is it a selfish arrogant thing said as a unitentional jinx? Or is it a resignation of the little bit of influence and care that you've provided?
Of all the slogans of parting, why would we chose this phrase? Do we mean what we say? Or is it not considered as it leaves our lips, that we are saying not the 'I will miss you, until we meet again' that we hoped to say, but a heartless 'Fend for yourself' instead.

Until we meet agian, I will miss you.