One book that had a huge impact on me was The Power of Full Engagement  by Tony Schwartz and Jim Loehr. The book’s thesis was simple: time-management doesn’t work because your energy is more limited than time.
Before the book, I used to get frustrated with my inability to follow my own schedules. I’d carefully carve out chunks of time for studying, working on my business, exercise, reading and more. But then I’d fail to follow it. I’d break down and wonder why I couldn’t be as productive as all those other people I admired.
Reading the book clued me into a constraint: that any sustainable workload had to be balanced in terms of energy spent and energy recovered.
Since discovering that constraint, I’ve built systems into my life that make sure I’m working sustainably. During the MIT Challenge , for instance, I often had to spend 8-12 hours a day studying. But I never once worked in the evening or on weekends for the entire year.
Accepting, Not Removing, Constraints
What’s interesting to me isn’t the book, although it’s a good one, but that it was an improvement which came from accepting a constraint, not freeing myself from one.
The stereotype of self-improvement is that it contains a lot of wishful thinking about liberating yourself from imagined constraints. That is, it’s fears, traditions or lack of the correct method that prevents you from achieving your full potential. If you could only eliminate these harmful constraints, you’d live a fuller, better life.
But interestingly, for me, I’d say about half of the best insights that helped me live better have come from recognizing hidden constraints rather than realizing old ones were illusory.
Habits are another great example. The basis of much of the habit-changing methods myself and many other have used comes from recognizing just how hard it is to change your behavior. Why is something as simple as going to the gym every day or flossing regularly so hard to stick to?
The solution comes from recognizing an additional constraint—namely that your life is silently guided by all these automatic, unconscious behavioral programs. Seeing that your willpower is weak and generally only effective at very short-term bursts of behavior change hardly feels empowering. But adding this additional constraint makes it possible to engineer plans that will actually produce long-term differences.
Growth Mindset and Finding Hidden Constraints
Growth mindset  has gotten a lot of popular support recently (and some criticism ). The basic idea is simple: if you believe your abilities and talents can be improved, you’ll perform better than if you believe they are a fixed constraint that must be accepted.
On a general level, this is probably true. If you believe everything is fixed, then it’s going to be pretty hard to summon the determination to work hard at it. Since working hard matters regardless, a general belief in growth will outperform a general belief that growth is impossible.
However, on a more detailed level, it may be the case that broadly believing everything is improvable isn’t the best approach. Accepting some constraints may help you focus your energies on the things which are actually most susceptible to improvement.
Which Constraints Should You Accept?
The best constraints to accept seem to be, first, the ones which actually exist.
Schwartz and Loehr’s book is based on their coaching experiences and an analogy with athletes, not hard science, so their theory could be wrong in some important ways. However, more basic research by Baumeister on ego depletion  seems to support the idea that there is at least some internal resource that the brain is trying to manage when deciding to exert effort.
Habits also have a scientifically verifiable basis. Starting with Pavlov’s dogs, we know that many behavioral patterns are conditioned automatically. Even if the science doesn’t provide the exact details for the best way to start a new habit, the idea of habits as a broad constraint on our behavior is pretty solid.
Other constraints are more controversial.
Consider intelligence. Wikipedia states that the heritability of intelligence is roughly 50-80% . But, cognitive psychologist Daniel Willingham states in his recent book here , that the consensus has shifted to thinking that intelligence is “probably mostly environmental”. Even if it is 80%, heritability doesn’t imply it can’t be modified . So what is it? 80% genes? Mostly environmental? Largely fixed? Largely malleable?
Intelligence itself probably isn’t a single attribute. It might be more like a collection of different abilities, all with different degrees of fixedness. General-purpose working memory and fluid intelligence are probably difficult to improve. Task-specific working memory and background knowledge are probably a lot easier to improve.
I’m not an intelligence researcher by any means, but as an interested layman, I find the scientific debate to be quite confusing. For the average person who isn’t interested in digging through the research, what chance do they have at determining whether they should treat their intelligence a constraint to accept or improve?
Intelligence is a particularly well-researched example. Other possible constraints you consider in your life may have no research at all. The decision to treat it as fixed or something that can be modified therefore amounts to a personal assessment.
Experimenting with Constraints
Since the evidence on whether a constraint is real or imagined is often murky, I think it pays to experiment with your strategies.
Perhaps you’re a somewhat introverted person, but you want to meet a romantic partner. What should you do?
One experiment would be to try improving on that constraint. You could go to bars and social gatherings and try to improve your ability to socialize in group settings. I know a lot of people who were self-proclaimed introverts who this strategy worked for.
Another experiment could be to try accepting the constraint and working with it. Maybe you get your friends to help set you up, or try online dating where you can meet people one-on-one. Instead of fighting your natural instincts, use the constraint to focus your strategy into areas where it doesn’t matter as much.
Or imagine you want to start a business, but you feel you don’t have the time to start one.
One experiment would be to improve on this constraint. Set aside time to work on your business on top of your normal schedule and deal with the intensity. Maybe you’ll enjoy working on the business so much that you’ll realize the constraint was imagined and you can get work done and build the business simultaneously.
Going the other direction: you might experiment with the belief that time is a real constraint. That might push you to request a brief leave of absence from your job—giving you a deadline to get your business up and running.
What all these situations have in common is that there is some ambiguity about the nature of the constraint: it might be rigid, flexible or somewhere in between. Testing out accepting and improving the constraint can sometimes help you resolve the question of what is the best approach to pursue when experts and science cannot.