Part of it is motivation. Why bother leaving, if I don't have a particular destination in mind? There are other things I could be doing that seem more important.
The other part is that I fall into patterns really easily. If I don't have a set destination in mind when I leave my apartment, I often just end up at the subway stop I take to get to work.
The other part is that I fall into patterns really easily. If I don't have a set destination in mind when I leave my apartment, I often just end up at the subway stop I take to get to work.