Not every idea has to be attached to a justification. There is nothing wrong in being inspired by a whim. Some of the most constructive innovations in history have emerged as a result of someone, somewhere, following a feeling. But while there is nothing wrong with spontaneity, we surely owe it to ourselves and others just to stop and double-check for a moment before we proceed. Think 'What's good about this?' But, 'Might there be anything bad about it?' If it passes that test, go ahead.