Song writting... Sometimes I'm playing guitar and, suddenly... something comes a up, like a cool sounding riff! Wow, this could be a good thing to work on. In my case, it's curious cause I start imagining almost the hole song... So I work on it for some time, it can be minutes, hours, days! In the end you can reach two conclusions. Either it sucks, and you feel like you've wasted your time, or... It could be your next big hit!! Go with your feelings.