A common misconception with exercise is- "If I can't workout at least 2  times per week then what's the point working out at all?"  There's a huge benefit to working out once a week compared to nothing at all.  First you have to understand the hardest part is getting started!  Making the effort to change your normal daily routine to include 30 minutes of exercise is a challenge for many people, even if it's only once a week.  So by including one exercise session a week,  your  building the foundation of a major lifestyle change.  The idea is to make it a part of your life not a chore that you dread and hate doing.   Getting into a consistent routine is much more important in the long run than working out heavily for a couple of weeks and than burning out . 
So start small, a simple walk in the morning or a jog at night and learn to appreciate what a little exercise can do for both mind and body.