Kick back. Relax. Here --have a glass of whisky (unless you're a non-practicing alcoholic or a teetotaler, in which case, let me make you some tea ...).
We've all had them. Those long days. Those looooong days. Those looooooooooooooooooo- *gasps* -ooooooooooooong days. They come and they go, and then, they come back like some kind of rash that didn't respond well to ointment.
What do you do on those days? I'll tell you what you don't do: you don't fight it. Makes it worse. I can tell you from experience (and by 'experience', I mean today).
Great. Don't fight it. Now what?
Get yourself some mindless music or angry music or soothing music, depending on your mood. Socialize or don't socialize, depending on your mood. Go to whatever your happy place is. At the moment, my happy place was Twitter for a little bit where I could be loud and weird, and in a few minutes, it will be someplace quiet and alone to read. I might exercise to get some endorphins --I might not. The point is, you do what you feel you need to do for you in the moment to let the day slip away.
You have people depending on you? You are a caretaker of some kind? Either get a little space from the serious duties or make them fun (silly them up a bit --why not?).
*Note: The title of this post is "After A Long Day At Work". Life is work, so if you've had a long day of life --not work-dependent --that counts, too. Take care of yourself when and as best you can.