Oh, I don't know though. Maybe this is a metaphor for all kinds of extremes. Reason and faith, abundance and shortage, love and loneliness. It's normal to have a degree of both. Wanting more of one or less of the other than you have is also perfectly normal. Needing--needing--all of one and none of the other is a sign of something wrong.

With this part, I very much agree.
Needing lots and lots and LOTS of light is usually a sign that something is very wrong - either with your eyes or your serotonine levels... (see winter depression and how a visit to a solarium can help there, provided they use UVb radiation along with UVa)