I think it's also how much of the Now we perceive and are aware of, as opposed to being caught up in thoughts and emotions of things that have passed and things yet to come, and of how things should or shouldn't be as opposed to how things just are.

Awareness is a somewhat limited capacity, and the less one trains awareness the less capacity one is capable of utilizing. So having awareness swimming around in places other than the Now certainly detracts from the rich experience life has to offer.