As total eclipse says, this triggering of emotions is likely associated with depression,there are a range of ways to get help, I hope you find something that assists you and you find a way to feel better.
As for why saying these things out loud or to oneself causes emotions to trigger. Some suggest that the way we think about events in life has an impact on how we feel, this is what's taught if you see a cognitive therapist. Eg two people lose a job one thinks "i'll get something sooner or later" the depressed person may think "with bad economy i'll never get something, I'm such a failure etc" these thoughts are linked to how you feel, examining these thoughts more rationally is what these kinds of therapists would teach you. There are other theories too I don't think any one is completely correct.
Of course examining your thinking is not always that simple when your in great emotional pain, and I don't think there's one easy answer or solution as to why we feel the way we do.