Our negative self-talk is usually automatic. It is not something we consciously think about, but it just "kicks in" whenever there is a triggering event.
Negative messages and stories tend to be on a "tape." In other words, once an event or a word triggers our reaction, the tape begins to play. It can go on and on, repeating the same negative message in our minds, sending us into a tailspin that can last for hours, days, or months.
Negative thinking is usually irrational, but to you it sounds like the truth. You have deceived yourself into believing a lie, and sometimes only a close friend or a counselor can point out the deceptiveness of the message you are listening to.
Negative tapes can lead to panic attacks, obsessive thinking, and phobic reactions. Just like bad physical habits, sometimes our mental habits cause us to become sick or out of control. Negative self-talk can also lead to serious problems when it remains unchecked.
(From The Complete Stress Workbook by Thomas Whiteman, M.D., Sam Verghese, M.D, and Randy Peterson)