Free time is harder to come by than you likely imagine. A recent article in the Harvard Business Review brought up the term "future time slack," which is the belief that you'll have more time in the future than you do in the present. This is the reason so many of us are inclined to postpone commitments for weeks or months-- we just assume we'll have more free time in our schedule then.
The term "future time slack" was first coined in a 2004 study published in the Journal of Experimental Psychology. Study authors demonstrated that people think they'll have more time in the (relatively near) future, but roughly the same amount of money.
The researchers put it this way: you think you're unusually busy now and will be less busy soon; but you don't assume you're unusually broke today.
Yet, research suggests that people who value time over money tend to be happier, possibly because they work less and therefore spend more time on activities they enjoy.
The moral here is really just not to wait to do certain things because you'll likely have the same amount of time then as you do right now.