How many times does an artist stare down at that blank piece of paper thinking "What on earth do I paint Where do I put my first mark?" More often than you would imagine! It happens to all creative people actually, from visual artists, designers, poets, through to musicians and writers.
When this situation arises, you are in the grip of creative block. When you wrack your brains to come up with ideas but just can't seem to. There may be contributing factors to this state, such as tiredness, depression, environmental, physiological or psychological issues. On the other hand you could just be experiencing a period of simple low creativity.
When this happens there are a few things you can do to restore your creativity levels at will, however what you must not do is worry or fret about it. If the worst comes to the worse and you don't seem to be able to produce any work, simply regard the period as a 'holiday' or a rest. Your creativity level WILL rise again. In the meantime, utilise the time spent not creating to do positive things anyway.
Once you are ready to start working again you will know it instinctively.
"ALL ARTISTS GO THROUGH PERIODS OF 'CREATIVE BLOCK' -- IT'S NORMAL, BUT AFTER ONE SUCH EPISODE, THERE ARE WAYS OF STIMULATING IDEAS AND GETTING THE CREATIVE JUICES FLOWING AGAIN."