Doing a spell a second time can be beneficial if the first casting was not done properly. I would wait at least one moon cycle before attempting the same spell again. Try to figure out what you did wrong when attempting the spell the first time. Many times it is due to a lack of energy that caused a spell not to work. One must always gather enough energy to manipulate in order for a casting to work.
The other problem could be that the spell is not feasible or realistic. Remember magic works when done for a realistic reason and is followed by the mundane actions to bring about the change. You can't do a spell to help you ace a test when you don't bother studying for it.