How Long is a Line of Poetry?

I have recently hit a surprising wall in my writing practice. One of the things I had thought I was good at was knowing where to end lines - one of the comments that I received on the poems that I submitted for my degree was that my line endings were extremely well judged. But of late I just seem to have lost the art of knowing where to end lines. It's like suddenly forgetting how to swim when you at the deep end of the pool. The trouble is that the more I worry about it the worse the problem gets. I don't know what's wrong with me - why have I suddenly become incapable of judging where a line should end? Is it a crisis of confidence? Is it a sign that I should be looking even closer at my writing style?

Part of the problem may be that over the years I have changed the way that I use line endings. When I first started writing poetry my lines tended to be short, more like those of Lorca, but over time and as my own style and voice developed, I began to make my lines longer and longer. I have found that in my more recent writing I am wavering between long lines and short lines, and have lost faith in my ability to use enjambment successfully. Maybe it is time to go back to basics and do some reading about line endings and line length. I guess what might also be helpful would be to go back and look at how I used line length in my older poems and why it was successful.