One of the main advances of the Prospect Theory by Kahneman and Tversky was, that it proved the former ideas about utility wrong. Before Prospect Theory, utility (subjective value) was believed to be about objective states in the world (e.g. having two million being double as good as one million). Prospect Theory showed it is actually about changes from a reference point. One could say it is "the theory of relativity of psychology" (this is a joke). What it means is: Two million is terrible if you were a billionaire the day before. It is crazy positive if you had an average income before. It also showed that experiences of losses are more painful than subjective gains are positive. And both gains and losses follow the classical psychophysics effect of diminishing sensitivity. Meaning that double a stimulus doesn't have double the effect.
So how does stoicism fit into that picture?
What we learned from Framing effects is that people passively accept a given wording and therefore what's relevant about an situation and reason from that given framing. They also passively accept the status quo as their reference point.
Stoicism uses mental effort to create an alternative reference point instead of passively accepting one. It is about actively and effortfully computing alternative worlds to set a different reference point and be happy about what you have and surf the waves of uncertainty. This also helps to overcome hedonic treatmill and stay continuously awake and aware about all the blessings you have on a daily basis.
From this mental state the ups and downs of daily life are experienced from a constant gratitude and joy about what is. It achieves tranquility and lessens negative experiences.
We are adapting very quickly to what currently is and get blind towards it. Stoicism means to open you eyes again.
I recommend the book "The Guide to the Good Life: The Ancient Art of Stoic Joy" which explains how stoicism is not about banning emotions but experiencing joy and the techniques to get there.