The Fountainhead has many flaws (IMO) but a scene I remember very well that I recall often, is the one where Peter Keating finally reaches the top of the firm, sits in his office, and starts crying. To me, and I guess to the author, it represents this aspect of having externally defined goals (as opposed to personnaly/intrinsic defined) and how unfulfilled you feel if/when you achieve them.

People (me included) often get confused and think that their goal of climbing the career ladder or being able to afford the nice <anything> is goal set by themselves only, when in fact it is a goal most likely induced by society and/or to reach a given social status. If you pause for a second and think honestly about your current goals you can probably identify the ones that are truly yours and the ones that are expected by society.

In the book "The subtle art of not giving a fuck" there is in addition to that the notion of open ended goals as a rule of thumb of good goals to have. And this to me is probably the equivalent of "constraints" in this essay. Make sure the goals you follow are set by you and not expectations of society and try to make and formulate them as open ended goals.