Working at a startup is like being on a rollercoaster. Some days you're high in the skies, some days you're down in the mud, and in between there is a constant grind of repetitive, often boring work. Many people put it up with it because they are gambling on a big pay-off, or are trying to change the world.
Lately, I've been learning to appreciate the journey more and more. Starting a company and building it up while overcoming hardships and uncertainty is challenging and fulfilling. It can also be depleting. Persevering while keeping an eye on the goal is possible (and I've done so for several years), but it's much better to be able to enjoy the journey as well as the results. Those years we put in, we are not getting back.