I think I've written on this before but I wanted to revive the debate.
In several courses this semester my professors in various fields (anthropology, philosophy to name two) have stressed that the concept of personal identity doesn't work. That it is fundamentally flawed when you consider all the facts.
The argument is as follows: Personal identity implies that there is SOMETHING about your mind (Note: We are going to leave the concept of the human body aside for a bit) which remains constant from the day you're born till the day you die.
It then asks people "What remains constant"? And what you find is that all of the logical answers rely on socially constructed ideas.
Someone raised in isolation of society would still have the cognitive tools of memory, of thought etc. But they would never claim that these things remain constant over time and lead to a conception of "personal identity" on their own. Im not sure about this, but it is my belief that someone raised apart from society would never think to themselves, "I want food" or "I'm hungry". They would simply be hungry and get food. Feel free to disagree... but support your position please.
Once you start realizing that individuals are really just collections of actions and systems which change over time your entire perspective on life dramatically changes.