I guess it depends on what you practice. Scales and modes are meant to help you find the notes you need for your accompaniment to the song. Just playing a scale over a chord progression won't sound as good as using your knowledge of the modes to find a melody line. If you can sing or hum what you want to play, you can play it. If you don't have some idea of what you want to do before you start to play, you have less chance of success.