I mowed the lawn again

Well, I didn't do any exercise, no excuses, I've just been lazy in that regard. I did mow the lawn, but that's really not the point.

I think that my goals, or rather my motivations, aren't realistic. The problem is that I'm not really all that unfit. Even with the sedantry lifestyle that I've been living for the past few years I'm probably still in the top 25% or less of the population as regards overall fitness.

How can I motivate myselt to increase my fitness level?