My friend Kevin sent me an article, written by a fellow tech entrepreneur, that describes his difficulty deciding how to divide his limited time and attention. His thesis is that we often tell ourselves and others that we don't have time for something when what we actually mean, even though we may not acknowledge it, is that we don't have the attention to give. And I agree - it's a common sentiment.
Attention is just another way of saying our ability to focus cognitive resources on a task, and doing so is a matter of willpower. The last decade has seen the birth of research concerning this - a.k.a. ego depletion (APA 1, APA 2, Wired, You Are Not So Smart / Podcast). The gist of said research is that willpower is both finite and variable. Finite meaning that our willpower is limited and variable in that the amount of willpower we possess can be altered by behavior.
As to "having time," in research surveys people report having less leisure time than ever, but in fact the opposite is true (thanks washing machine!). So what's going on? All else equal, earning higher wages makes us feel more anxious about our free time and we feel we have less of it even though the opposite is true. Researchers have termed this effect time poverty.
To bring this back to the original article - the author mentions not wanting to take on another responsibility that divides his attention which reminded me of a reddit AMA (ask me anything) from earlier this year with Elon Musk. He replied to a comment asking how he managed to become proficient in so many technical areas:
What Elon is saying is that changing mental tasks takes time. So much so that he can't focus on a given task as singularly as he was once able to, and when he does he spends a lot of time readjusting to said task.
This leads us to a TED talk about how those in creative fields need large chunks of uninterrupted time to be productive and how it conflicts with managers schedules which are typically broken into 15 minute increments.
This is a nearly endless subject. I think a lot of it is driven by the fact that most other aspects of our lives are being completely altered, made faster, more efficient, etc. while time and its management has hard to move boundaries which all of us are increasingly bumping up against.