Can't Get Motivated at Work — What to Do?

I can't seem to get motivated to work lately. It's been going on for a few weeks. I used to be a really hard worker — I'd work late all the time, all hours of the night, whatever it took. Now I just do the bare mininum. I don't like being this way, but I don't know what my problem is either – if I'm depressed or just lazy or what. I have a really good paying job and I know I should be grateful – I am grateful, but I just can't seem to get my butt in gear. Do you ever feel this way and how do you deal with it?

Suggestion:

At some point of life, people come to the realization that life is pointless. That's when everything else appears to become boring and pointless. Some suicide, others continue trying to find an excuse to live.
Looks like you've just reached that phase.

Give yourself a reminder. Think about the reason for you living. Is it so that you can earn and support your parents and siblings? Or something else?
Forget about what life is and it's purpose. Nobody has found out and nobody probably ever will. Think about what you want to do in life (in the long run). Do you want to be a home-maker or do you want to achieve a certain post in your company? Form a goal that may take you a few decades to achieve, figure out what you have to do to achieve it, and go toward it full steam. That's what will get you going. Good luck!

And like the first person said, if your job or your manager isn't really bothered about the work you do, then the best thing you could do is to go to another company where people believe in what they do and are engaged in their work.