As writers we have all hit writer's block at one time or another. My advice is to put it away and come back to it in a few days. This allows you to refresh your vision and mind. It gives you a clear perspective on the topic on hand. This doesn't always help, I'm not going to lie, but it can be very helpful. Sometimes I've come back two years later and finished the tale. Is this bad? I think not. Writing is a mind of its own. Flow with it. Don't force something that just just fight well because you're impatient.
If you are writing an essay for school, I definitely don't recommend wait until the last second. It never ends well. One of my teacher advises to have it finished at least one week before it's due. It gives you time edit and revise.
I'm writing a story about a dangerous love and I totally hit a block. I'm still not sure what to do, but in time I will. Even if it means starting over. But if anyone has any ideas for a story involving a "good-girl" and the son of a mob boss, I would really appreciate it! :)