Musar zu Kohelet 2:10

Why then should we now adopt new decrees which they did not see fit to enact? Furthermore, there is no end to this matter. Thus, a man would soon be desolate and afflicted, deriving no enjoyment whatsoever from this world, while our sages, of blessed memory, said: "a person will in the future be held accountable before G-d on all that his eyes beheld and he did not want to eat from it" (Yerushalmi Kidushin 4:12). This is even though it was permitted to him and he had the ability to do so. They brought support for this from scripture: "all that my eyes desired I did not deprive them" (Kohelet 2:10).

Separation in the laws is to always be stringent in them. To be concerned even for the view of the solitary opinion if its reason has grounds, despite that the Halacha does not follow this opinion. The condition, however, is that his stringency not become a leniency.