Let me try an experiment in applied philosophy: is one's sense of being a subject enduring through time going to enhance one's future happiness or not? I'll sketch the two options in a rather extreme way:
1: Enduring Subject. I have an excellent memory and my memories play a major role in shaping my actual life. I am also a self-narrator: I regularly rehearse and revise my interpretation of my life. I am a great planner and knit up my life with long-term projects. In fact, I enjoy remembering, rethinking and understanding past events and I enjoy even more thinking about the future and trying to do my best in order to achieve what I would like to (the first part of this description has been adapted from Galen Strawson, 'The Self', pp.14-15). I can also add that I have somehow been trained to be one, insofar as my father writes/used to write a diary and likes/used to like to talk about his past life and to 'understand' it. My mother does/did it much less, but appreciates/appreciated it.
Nonetheless, I never thought of that as a particular ability, since it seems spontaneous to me to plan and remember. I also tend to think that this made possible many important decisions in my life —the ones I am now happy about. For instance, if I had not been a planner, if I had just jumped from one thing to the other (again, Strawson), I would not have decided to interrupt my South Asian studies in order to study Western Philosophy. I did it because my long term project was to study Indian philosophy and, hence, I knew I needed a better philosophical training.
People who do not remember, are likely –again, in my opinion– not to learn from their mistakes and, hence, to repeat them again and again. They might marry beautiful women because they are at first sight fascinated by beauty, only to then understand that they in fact would have preferred a caring one. Similarly, people who do not plan may not be able to finish their studies or to engage in whatever activity is not at every moment rewarding –and this category includes, in my opinion, most really significant jobs.
2. Momentary Subject. Other people, and G.Strawson claims to be one, "have a very poor personal memory. And it may not be simply poor. It may also be highly quiescent, and almost never intrude spontaneously into their current thought. […] They have no early ambition, no later sense of vocation […]. Some merely go from one thing to another". More in detail, Strawson avows that "Using 'Me*' to express this fundamental way in which I think of myself, […] I can accurately express my experience by saying that I do not think of Me* as being something in the future. It is also accurate fo shift the 'not', and say, more strongly, that what I think of as being in the future is not Me*". Assuming that such an extreme case is possible, this would lead to some unwanted consequences, such as the ones I listed above (but also teeth cavity: since one does not identify with the subject who will later experience pain, why should one care about cleaning one's teeth?). On the other hand, it might have its pros: since one does not think of oneself as existing in the future, one is not afraid of examinations, loss of one's job, loosing a beloved person, etc. Further, one does not regret past events, nor does one have to bother about planning one's future, especially if this involves painful decisions. More radically, a Buddhist might argue that one is many steps ahead in the path away from 'I' and 'mine'.
I know, the analysis is too crude, especially insofar as (in 1) it presupposes the existence of a self when it describes the possible shortcomings of position 2. To say the least, one might argue that it is senseless to try to learn from one's mistakes, since there is no special link between, e.g., 'my' mistakes when I was 13 and 'my' mistakes now. Instead, it might be better to investigate on 'common mistakes' of people in a certain age-group or social class, etc.
What do readers think? I'm curious to know about insights from the latter kind of experience.