I am feeling a bit shattered at the moment, that much is clear. I am introspective – it is good, but I can get self-critical.
I feel get down on myself for feeling insecure (or, in other words, feeling insecure about feeling insecure). What the hell is that?
People say, “you have to build up your own confidence” and I wonder what to do in order to achieve this.
I am doing a lot of things, come to think of it.
– medical research, travel on own, running (plus a marathon), upsetting the apple cart re: an unhappy marriage. These things I never envisaged I would have the strength or ability to do, yet I am doing them.
By comparison, the other things I want to do, say, going to a music concert or salsa class or a good restaurant by myself, are relatively easy, come to think of it.
So I will go and do these things. AFTER I have finished my paper. And moved. Priorities.
Run – done. Thoroughly enjoyed it. So did the dog.
Demons, dancing, doctorates, debauchery. 
Confidence is a weird animal. It comes and goes, often we know not why (or at least that is my experience). My only advice is to concentrate on the things that need to be done, busy yourself with these and do them well, that will raise confidence. Then, the rest of the time concentrate on distracting things that you enjoy.