~ Paul Henri Thiry Holbach in The System of Nature (1770)
This quote by Baron D'Holbach dates from 1770 yet it reflects, I think, a quite modern view on happiness. The first part of the quote, "Happiness to be felt cannot be continued", reminds me of something which is known as sensory adaptation which means that our nervous system changes its responsiveness to a constant stimulus over time. For example when your neighbor is working on his house and making drilling noises all day, at first you may notice this very clearly, but after some time you may not notice it so much anymore. At the end of the day you may even suddenly realize that you have not thought about the noise all afternoon and have not consciously noticed it at all. The same might apply to happiness. It seems impossible to keep feeling it all the time. What context would be such that it would allow us to constantly feel happy? It is hard to think of one. It is more likely that we are capable of experiencing episodes of happiness at best.
If that is true, the second part of the quote becomes interesting: "Labour is necessary to make intervals between his pleasures." If happiness needs to be interrupted in order to keep on being experienced, what is a good way to interrupt it? D'Holbach suggests that work could play that role. This reminds me of the work on flow by Mihály Csíkszentmihályi and his colleagues. Flow is an intense experience of involvement in a day-to-day activity. Flow happens when people have clear goals and when there is good balance between the perceived challenges of the task at hand and one's own perceived skills. When flow happens there is, among other things, a temporary loss of the feeling of self-consciousness. Therefore, when we are in flow we aren't particularly happy or unhappy. Instead, it seems we seem to have become temporarily one with the situation or the task. Work, in particular, offers opportunities for being in flow. Therefore, work seems like an excellent activity to interrupt happiness. And it has the potential to interrupt happiness not by unhappiness but by the absence of self-consciousness and therefore, the absence of both happiness and unhappiness.