The psychasthenic has insufficient control over their conscious thinking and memory, sometimes wandering aimlessly and/or forgetting what they were doing. Thoughts can be scattered and take significant effort to organize, often resulting in sentences that don't come out as intended, therefore making little sense to others. The constant mental effort and characteristic insomnia induces fatigue, which worsens the condition.

Whereas the hysterias involved at their source a narrowing of the field of consciousness, the psychasthenias involved at root a disturbance in the fonction du reél ('function of reality'), a kind of weakness in the ability to attend to, adjust to, and synthesise one's changing experience (cf. executive function in today's empiricist psychologies).

Karl Jaspers preserves the term 'neurasthenia', defining it in terms of 'irritable weakness' and describing phenomena such as irritability, sensitivity, a painful sensibility, abnormal responsiveness to stimuli, bodily pains, strong experience of fatigue, etc. This is contrasted with psychasthenia which, following Janet, he describes as a variety of phenomena 'held together by the theoretical concept of a 'diminution of psychic energy'.' The psychasthenic person prefers to 'withdraw from his fellows and not be exposed to situations in which his abnormally strong 'complexes' rob him of presence of mind, memory and poise.' The psychasthenic lacks confidence, is prone to obsessional thoughts, unfounded fears, self-scrutiny and indecision. This state in turn promotes withdrawal from the world and daydreaming, yet this only makes things worse.

'The psyche generally lacks an ability to integrate its life or to work through and manage its various experiences; it fails to build up its personality and make any steady development.' Jaspers believed that some of Janet's more extreme cases of psychasthenia were cases of schizophrenia.

(http://www.autoadmit.com/thread.php?thread_id=2246392&forum_id=2#23127376)