Be careful not to underestimate the influence of the ambient light while you're editing your photos.
I've seen many people comment that when they edit photos at night, then look at them during the daytime (or vice versa) they look markedly different.
Of course, when you edit some photos (especially if you're tired), then look at them again a few hours or days later, you're always going to notice some things you'd like to do differently or better. That's human nature, I guess, and in a way it's a good thing - while you're perpetually critical of your own work, you'll keep striving for improvement. And as long as you do all your Photoshop editing with layers, it should be very easy to make whatever adjustments you need.
But I'm not here to pester you about layers again. I want to discuss light. The light that's around you while you're doing your post-processing.
Some people say you should edit in the dark. I mean, really dark. Other people don't say "dark", exactly, but they say that the computer screen should be the brightest thing in the otherwise dim room. Me, I think that's completely ridiculous. What kind of idiot stares for hours directly at the brightest light source in the room? How is that good for you? And what about if you need to jot something down, or read something you jotted down earlier? And how on earth are you supposed to compare your prints to your screen to see if your calibration is accurate? (Actually, the answer to that last question is: you're meant to buy a fancy viewing booth. I've got better things to spend my money on, frankly.)
Ok, I realise that last paragraph was a bit of a rant. If you like to edit in the dark, and it works for you, go with it. But any time somebody asks me, I always give the same response: "I think you should only edit in light that you'd be happy for your kids to do their homework in." You wouldn't like them to be risking eye strain by writing in too-low light, and I don't want you to risk it either. I hasten to add I have no scientific basis for this - it just seems sensible to me.
Anyway, what's MOST important about your light is that it's consistent. It's got to be the same every time you edit. And that's not always an easy thing to achieve.
Me, I'm incredibly lucky. The bloke who owned our house before us was a musician, and he built himself a windowless (and soundproof!) room downstairs. When selling, the poor old real estate agent must have been wondering "how the heck am I going to market a windowless room??". But it's perfect for me! I've got some nice "daylight" (6500K) bulbs in the ceiling, and no matter when I'm editing - day or night - the light is exactly the same. It plays a huge role in the consistency of my work, and that's important.
Actually, the middle of the day isn't such a problem - not here in Queensland, anyway. That light is pretty "white". But it's the golden tones as the afternoon goes by, and turns into evening, that are problematic. Lovely for taking photos in, not so good for editing.
Not many people will be as lucky as me, I guess. Some of you might be able to find a windowless nook in your home, away from that nasty changing sunlight. But most of you will have windows to contend with. So you have to do the best you can.
Heavy curtains are the best answer, of course. Cardboard is also good, but doesn't flatter your house! Anyway, you've got to block out that outdoor light, and install some good indoor light. As I said, I had no trouble going to the lighting store and asking for 6500K bulbs. They're very standard. Then it doesn't matter when you're working - it's all the same light.
One more thing to mention. Often people ask me what I think about laptops for editing. I don't like them. Not because of the laptops themselves (yes, some have really bad screens, but others have perfectly good screens), but because of the very thing that makes them attractive - their portability. If you've got a laptop, you're tempted to edit on the couch, or in the hammock, or wherever. Please be careful about this. Give a thought to the light you're in, and what impact it might be having on your edits.