It is fundamentally human for us to lose track of why we’re doing what we’re doing while in the middle of long-term projects. From an evolutionary perspective, exhaustion prevents you from behaving in ways that lead to inefficient use of resources. More generally, exhaustion is a form of optimization related to a classic reinforcement concept called exploration-vs-exploitation, where an agent must decide whether the benefits of discovering knowledge eventually result in a larger cumulative reward than the cost of exploring unknown portions of the environment.
At the end of the day, exploration-vs-exploitation is inherently subjective, depending entirely on what your goals happen to be, both long as well as and short-term. We have a tendency to prefer short-term reward due to the discounted cost we assign to problems that aren’t an immediate threat in our current environment. We perceive threat as exponentially decaying over time relative to our current situation, because the problems we assume will occur sooner rather than later have a smaller buffer-period to think of solutions.
This is obviously a good mechanism if you’re being chased by a lion, but in modern society we associate a lack of long-term consideration with words like inattentive, scatter-brained, and stupid. Whether or not this implies something about the person or something about society, it is generally good advice to plan ahead.
Perhaps even more importantly is to sustain your long-term goals over time. This is easier said than done because we base our judgement about the worth of actions in relation to the expected reward, which we know is something that decays exponentially with time, thus our decisions are heavily based on nearby-present forecasts and expectations. This contradicts our superegoic drive to better ourselves, which is inherently tied to further acknowledgement of the future.
To conclude I’d like to say partly to you and partly to myself that achieving long-term goals cannot be broken down into strictly long-term or short-term consideration. It requires every level of the brain to work in harmony, therefore it requires a conscious effort toward psychological well-being, a general understanding of the fact that all areas of life suffer when the mind is not at peace, and finally of the realization that you alone are responsible for the progress that you decide, or don’t decide, to make.