In literature, there are three main types of conflict that represent the problems we all share: man vs man (interpersonal problems), man vs the environment (survival related problems that no longer exist in our modern world), and man vs himself.

While you make an interesting case for saying that intrapersonal problems (man vs himself) ultimately have a cause in interpersonal problems, I’m not convinced. There are many things we do that actually put our interpersonal relationships at risk or put unnecessary strain on them. Things like becoming an entrepreneur or an artist with very little chance of success but a high level of personal fulfillment.

Achieving personal fulfillment doesn’t necessarily have to have another goal. It can be a goal in itself. Some problems just have to be resolved by man vs himself :)