I'm NOT a psychiatrist. I'm a psychologist, but my only real experience with Cymbalta was when my then 17-year old daughter was taking it.
As someone already mentioned, Cymbalta works on the norepinephrine and serotonin pathways, as opposed to many other meds which only work on serotonin pathway (prozac, zoloft). This is what makes it work better for some people. This is also what makes it much worse for other people!! My daughter is apparently sensitive to the norepinephrine pathway drugs, and had some bad psychiatric issues for a few days. So if it works for you, then great! If it doesn't work for you, keep in mind you may not be a good responder to norepinephrine pathway drugs (effexor is in this class too).
You SHOULD NOT abruptly stop taking any antidepressant meds, because lots of them can cause some fairly mild, but weird, withdrawal symptoms.