Right now, an estimated 18 million people worldwide suffer from some form of Alzheimer's; a disease that robs a person of their memories, and later their ability to cope with everyday tasks. Amnesia, on the other hand, is much more rare in terms of the full-blown 'who-am-I' variety but much more common than we realize. If you think about it our 'short-term memory' (memorizing a phone number for instance) is built in amnesia.
We actually forget the past all the time, whether or not we remember that.
So... Are we the past?
Some say that nothing is ever really lost; others say that nothing is ever real anyway. After all, our past isn't really about the events that took place, but how we experienced them. Our past is only as important as how it affects the actions we take in the present.
So... Are we the present?
We're not really the present either, but rather we use the present to connect to the world around us. Being without our past can be a blessing and a curse. We live for each moment directly, which is more powerful that being in the present, but living in the past. The curse though is that even the present moments are stolen away after they leave.
Who are we when someone forgets?
It may not be so tough being the one who forgets. After all, if it bothers you one moment, even that will disappear. It's much tougher for those on the outside... for them, the past still exists. Whole identities are tied into someone else's past as much as their own. With one person out of the equation, the relationship that once was, is now gone... and in many ways, so is the current relationship.
For those outside, living in the present moment is even more important. The insider needs more attention here. Often, the outsider is the only connection there is, if only tenuous... if only temporary.
What to do?
The best thing, for everyone, whether inside or out, is to love life right now. Connect to each moment and cherish it.
And let's not put all our identity in who we think we were... or who we even think we are. We're so much more than experience... and we don't have to remember that. We just have to BE that.