That's great. I think my total for a single day is 10,000. It can be exhausting.
Writer's block- assuming it isn't laziness, if you're experiencing it consistently, you may have problems with your plot that you haven't discovered yet. Or maybe your characters aren't quite right for what you want them to be. It's worth looking for plot holes and asking yourself questions.
And then there's the habit of writing- if you write a lot on a regular basis, you get your writing muscles in shape and it is literally easier to write more, more often. All I can suggest is to pay attention to the world around you, which is also a useful skill that can be developed- one day I looked at the front page of the paper, and saw in it the ending to a story I was writing. And another time the end of one book suggested (distantly) the end of another I was working on (of course, mine is way cooler). Also branch out of what you normally read or even watch. If you get desperate enough to hit a word limit (though it may not work for everyone) you might find yourself grabbing for whatever plot points are near at hand, and things will find their way into your story that otherwise you wouldn't have paid attention to.
