Achieving something now at the cost of future happiness is a dangerous choice. Not because of the consequences of doing it once, but because of the temptation to repeat it again and again, until the cycle breaks you.
The classic example: forgoing sleep to work a few more hours each night. You make a few more deadlines by sacrificing your health.
These days, I prefer to view success as something that I can maintain over time, not a singular accomplishment that extracts a toll down the line. After all, my ability to enjoy tomorrow is impacted by what I do today.
Related: Getting a big lead helps avoid costly short-run decisions.