I have a rosemary bush that is at least 4yrs old. It is stemmy and leggy on one side. I'd like to cut it back, but am not sure as to how far or whether or not doing so would hurt it. When would be the best time to prune. I love walking by it and having it rub against my clothes...it smells so good, so I don't want to accidently destroy it! Any advive would be very appreciated.