We live in a world in which who we are is defined by what we do. We are a role - parent, engineer, carer. Strip that away and all that remains is a who. That's the reward of solitude: a situation wherein you have nobody to bounce your 'self' off, nobody to define yourself in relation to, allowing you to surface.
Turns out that who you are is simply a sequence of reactions to experience - the external kind as well as that which bubbles up internally. Rather than terrifying, this should be seen as profoundly liberating.