compulsion to worry correlates tightly with depressed mood

There are some very interesting notions about depression from an ev-psych perspective here, the gist of which being that depression is "effort to reconstruct models of the world so that future action can lead to payoffs, in part through stripping away previous valuations that led to unwelcome outcomes". As a result depression results in "suspension of behavioral activity accompanied by very intense cognitive activity".

In somewhat more detail,

Depression should be precipitated by (1) a heavy investment in a behavioral enterprise that was expected to lead to large payoffs that either failed to materialize or were not large enough to justify the investment; or (2) insufficient investment in maintaining a highly valued person or condition that was subsequently lost (possibly as a consequence); or (3) gradual recognition by situation-detectors that one's long-term pattern of effort and time expenditure has not led to a sufficient level of evolutionarily meaningful reward, when implicitly compared to alternative life paths (the condition of Dickens' Scrooge).

In other words, depression is the manifestation of the brain calling a "Halt, melt and catch fire" event.

What I've been wondering for some time now is whether the causation can go in reverse - i.e. whether intense thinking about your life's overall strategy can be recognized by your brain as "that mood" and actually trigger the emotional ensemble associated with depression.

I can't think of any sensible advice, though. What I tend to do about decisions (mostly minor) that are waiting on further information is to put them into my GTD system with an appropriate "decide by" date, and annotate them with information as it comes in. I find this a big help in offloading concerns from conscious thought. I have no idea how that system would cope with a life-changing decision.