Recently read 'Altered Traits', plenty of other books, and I've been meditating on and off for 20 years, but I'm still stumped. 
(My history has mainly been round Goenka courses)

Why does meditation work? Why is it that even after what feels like a 'crap' meditation - barely able to focus - I still feel better afterwards? Lighter, freer, clearer in my head. 

I'm talking mainly daily practice here. Retreats can go many different ways! I sat this morning, feeling  pretty crappy - and now I don't feel so bad. It's so remarkable, and it nearly always helps. It really does seem true that the only 'bad meditation' is the one you don't do. 

Such a mystery. I don't expect any answers here, but any insights or thoughts would be welcome!

The human's natural baseline state of being is peace/clam/joy. Doing meditation can tap into that regardless of how clearly one knows this to be true.

• It stills the narrative babble consciousness of "Self" which is universally nerve-wracking. Someone ran a study where over 100 participants were given the choice to sit in a room with just their thoughts or to give themselves a painful shock to the finger. All participants chose electrocution. One guy shocked himself over 130 times.
• It temporarily nixes the cycle of obsessing with the Past/fantasizing about the future, which is nerve-wracking.
• Axiety is largely a byproduct if (1) and (2) above, plus irregular breathing.
• Mind enjoys being in charge for the first time since you turned 11 years old and handed the keys to your Self.

Hey this is great. Thanks both for your thoughts...

That's what we're here for.

P.S. I added a funny but true story to my #1, go back and read it again. ;) #SadButTrue

Oh damn, that's hilarious and a bit sad!

I would hate to be in any kind of solitary confinement without meditation (I'm sure it would be very tough even with)

I heard about that study too and I reacted similarly to Bill - it's the meditation that makes confinement a treasure. One thought that popped up was how weird people are. I thought "How bad could it be? It's just me!" (this was before realizing that there are no separate entities). "I would never..." and then it dawned on me how much time I had spent on social media and netflix in order not to be alone with my thoughts. I bet the electric shocks were more humane than some of those facebook discussions. 

Oh yeah - totally! So many distractions in our pockets now. This is interesting on that tip -

https://humanetech.com/podcast/
Tristan Harris going deep on tech ethics.

Thanks Michial - This is my favorite type of explanation.

Mind like a mucky 'snow shaker' toy, that you just need to stop agitating for a bit. All the muck settles to the bottom.

Nice and simple.