It's an interesting question. Certainly, received wisdom in my own family is that shared experience is what creates meaning in our life and memories. However, one can find many successful figures in history (Nikola Tesla, etc.) who were certainly 'successful', nominally happy, and relative or declared hermits. I've met real world hermits who seem content. One of the big European self-help authors got his start as an antisocial homeless person meditating on Buddhism. Discipline and a lifelong love of learning and intellectual exploration are not automatic traits... perhaps those without these types of developed habits find it harder to obtain fulfillment in relative solitude?