You have been working a lot lately, and there is much stress in your day. As a result of this, you aren't getting much sleep and you drink considerable amounts of coffee. There are many other people such as yourself out there, and they all share one common problem.
You come home after work, late at night. You sit in front of your computer, trying to read this node, and there it is again. Your eyelid starts twitching randomly. A twitch here, a twitch there, sometimes the left eye, sometimes the right eye. You go and wash your face with water but it doesn't help much.
Eyelid twitching falls into the catagory of eyelid spasms. Its exact cause is unknown. A slight spasm of the lower eyelid or even both eyelids is common and of no concern. It is known that the problem is related to stress, tiredness, the lack of free time, and heavy caffeine consumption. It's the way of the the body to irritatingly signify to you about your stress.
The solution is simple: Take a break, a vacation. Go to sleep, and try to sleep a lot.