What is Neuroticism?

In the Big 5 Model of personality traits, being a neurotic not only disposes you to anxiety and other negative emotions, but to spending lots of time ruminating about all those feelings. 

Negative feelings will lead a nuerotic person to either internalize, withdrawing into their insecurities and ruminations, or externalize, getting angry, irritable, or impulsive. In order to deal with this, they'll attempt to suppress negative feelings and risk developing disordered behaviors, which, essentially, are people’s ill-fated attempts to feel better.