A theory of mine:
Mood is often thought to lie along one main axis: at one end, euthymia (or mania), and at the other, dysthymia and lethargy. However, this is an oversimplification. Rather, mood lies along two (or possibly more) main axes: thymia and energy. The former ranges from euthymia to dysthymia, and the latter from lethargy to zeal, thus:
Mania | Anger
Joy | Angst
Placidity | Depression
In my experience, this is far more apt than a single axis, though perhaps the commonest moods lie nevertheless upon the diagonal from upper left to lower right.
In this system, one who has little motivation and energy is lethargic rather than depressed; one who has great rage and grief is dysthymic rather than depressed. Only one who has both symptoms is truly depressed. This is of note since both dysthymia and euthymia can be powerful, driving forces, but one must be zealous for this to be so. The real problem is lethargy.
This is the SSRI's dirty secret. Some studies (1,2) have shown that SSRIs can cause blunted affect. Of course, this may be better than severe, crushing depression, but in milder cases it may not be preferable.
I AM NOT A MEDICAL PROFESSIONAL; THIS IS NOT A PROFESSIONAL MEDICAL OPINION. Talk to a psychiatrist at once about any mental problems, and value his or her professional opinion over aught posted by some guy on E2.