I would defnitely start with a shorter piece if things get boring on a longer one, but don't be discouraged. Once you find that spark, that one thing you need to write about, it gets easier... a little...

My tip works for any story. Try to put your reader at the side of you as you experience the 'action' (there doesn't have to be blood or mayhem, the 'action' is what's happening). Write details that you may think aren't important at first. The overcast sky may make it difficult to see the traffic - and pedestrians - for example.