I think, therefore I am

I attended this lecture in the British Library where some motivational speaker talked about discovering the self. He asked, what made us individual entities? What is the self? A few hands went up, venturing some answers and the speaker promptly showed how nothing can really define the "self" as an individual entity. Not even our thoughts because every thought that comes to our mind, has already been thought of by somebody else... Obviously, I thought of the cartesian philosophy of "Cogito ergo sum" or I think, therefore I am. My self distinguishes itself from the others by its thoughts. Had Descartes got it wrong... I think yes, more so since I read the following paragraph from Milan Kundera's L'Immortalite:
Je pense, donc je suis est un propos d’intellectuel qui sous-estime les maux de dents. Je sens, donc je suis est une vérité de portée beaucoup plus générale et qui concerne tout être vivant. Mon moi ne se distingue pas essentiellement du vôtre par la pensée. Beaucoup de gens, peu d’idées : nous pensons tous à peu près la même chose en transmettant, en empruntant, en volant nos idées l’un à l’autre. Mais si quelqu’un me marche sur le pied, c’est moi seul qui sens la douleur. Le fondement du moi n’est pas la pensée mais la souffrance, sentiment le plus élémentaire de tous. Dans la souffrance, même un chat ne peut douter de son moi unique et non interchangeable.
Translation:
I think, therefore I am is a statement of the intellectual who underestimates toothache. I feel, therefore I am is a more general truth and concerns all living beings. My “I” does not necessarily distinguish itself from yours by the thought. Too many people, too few thoughts: we think more or less the same thing by transmitting, borrowing, stealing each other’s thoughts. But if somebody steps on my feet, only I will feel the pain. The “I” is based not on the thought but on suffering, the most elementary emotion of all. Even a cat who is suffering cannot doubt her unique and non interchangeable “I”.

True, isn't it?