More on the mechanics of decluttering:
Take out all your clothing and pile it on the bed. Get rid of anything that doesn't fit, that you don't like, that's worn out. Get rid of things that you just don't wear. Going forward, keep a bag in your close, and when you pull out something, look at it, and decide "nah" put it in the bag. That thing doesn't need to be in your life. Also, get rid of anything that makes you feel ugly, dowdy, or unattractive.
Institute a "one in, one out" (or "one in, two out" ) rule for most things. Only buy a new (whatever) if you're willing to get rid of at least one (whatever). You almost certainly already have enough of them.
The only problem with going through, say, a drawer at a time is that it doesn't give you a chance to see what you already have. So, for instance, if you're sorting through wine openers, make sure you put EVERY SINGLE wine opener you own in one place, and then make a decision about how many you actually need, and which one (or two) you're going to keep. I very strongly suggest sorting stuff by type and/or function, rather than by location. (This does mean that when you're sorting through, say, coats, you have to gather them up from all their locations -- front closet, bedroom wardrobe, wherever else you keep them -- so you can see them all at once.)
If you're really having a problem with lighting, you can look for a "SAD light" and sit by that in the mornings. Or go for a walk first thing!