ব্যাখ্যা
“Grapes are sour” is the expression we use when someone puts something down in a negative way or makes it out to be unimportant solely because it is unattainable to them. Oftentimes the term is used to signify resentment.
Bangla Meaning: আঙুর ফল টক।
Rationalization is the action of attempting to explain or justify behaviour or an attitude with logical reasons, even if these are not appropriate.
The proverb "grapes are sour" (rationalizing something as bad because it could not be attained) is an example of rationalization of behavior.
Rationality on the other hand is based on reasons given objectively and is not colored by one's perceptions.
Thus, it is concluded that The proverb, “Grapes are sour” is related to Rationalization.