I know exactly what he means. I constantly have to tell myself to venture out and try new things, take risks, etc. in my daily life as well as photography. (here I go applying real life to photography and not the other way around...) My wife and I recently wondered why our lives felt like they were going nowhere. We stood back, evaluated and figured out that we were too comfortable with our current situation. If we wanted things to change, we had to change. There's a much longer story that I could tell, but I won't go into it.
Anyway, you are probably very comfortable shooting still lifes. You know what you are doing and you can do it well. Sometimes venturing out into the world and trying something new can give you a new perspective on what you do best. For you, this could mean trying some really-out-there still life subjects or maybe 'still life in motion' as in shooting a still life of something that is actually in motion or 'life...still' and go out and include people and daily life activities in your compositions. I've found that in my own photography and graphic design, my work lacks that creative edge when I end up using a 'formula' for the way I do things.
Wow, I just talked myself through this, too, and gave myself some good ideas. Maybe I need to write more.