Finding our way back and then forward

In a Nichols and May skit, Elaine May plays a mother who wishes that her son would call and visit more often. She reports that she's going into the hospital so that the doctors can x-ray her nerves.
I've noted that, of late, things are going pretty well. My days are full with interesting and often useful activities, my mood is good, and I can often make and meet commitments - all signs that point toward health. I feel like I'm on my out of the woods, but I also know that I've felt like this before.
Even a momentary distraction can have one turned around and headed back into the underbrush. Yesterday evening, for example, a chance reminder of a difficult relationship at a former job was enough disorient me. It didn't last long and that's also part of the good news, that a bad moment doesn't always have to lead to a bad night, day, month. You get the idea.
There's a very good blog post over at Recovery, Well-Being and Purpose | Storied Mind, addressing this change of perspective, getting beyond survival mode and (back) into living with a purpose for a future.
One of the continuing challenges, though, is staying grounded, being able to observe and accept what's really going on with us, not just what we wish would or wouldn't be happening. 
Wouldn't it be great to have some definitive, external, verified, repeatable test that could a) diagnose depression, b) determine the severity, and c) chart our progress over time so that we could know if a treatment is making a positive difference.
Instead, we have to rely on the BDI and other self-reported measurements. It's a lot like those eye tests ("Which is better, 1 or 2?") where your ability to see clearly for the next months or years is dependent on making a fine distinction that you just don't know how to make.
There is some encouraging research, such as in these articles, Dr. Francis Lee Recognized For Developing Genetic Test To Guide The Treatment Of Depression and Possibility Of Brain Scan-assisted Diagnosis For PTSD A Step Closer. Other research (Early Brain Marker For Familial Form Of Depression Identified By Columbia Researchers) may lead to early identification of people who are greater risk for development of depression. (We'll leave aside the ethical, political, and insurance risks of such predictions for another discussion.)
Getting where you're going depends on knowing where you are. Or something like that.