Although I understand what lies in your question of developing a system, if I look at it a bit more I notice another potential layer of interpretation.
In sum, I think we do develop certain systems as daily coping mechanisms for both positive and negative stress we experience. Those who don't usually suffer from some depressive or other disorders or these disorders are the reason a person cannot adapt well enough for various daily encounters in the world (this is a bit chicken/egg question and depends on numerous factors for an individual, so I will leave it aside). These "mechanisms" involve both some more clearly established maneuvres (e.g. particular motivational phrases/yoga/certain songs/people to address), but also a wide array of different and not necessarily connected activities.
It seems like when we are brimming with negative thoughts and emotions, what happens is we somehow cannot find our feet at the moment and that always, even if deeply subconsciously, renders us restless and in with a dose of uncertainty. And this "uncertainty" ranges from something benign to more acute or chronic levels of anxiety. And this is where a "system" comes in. In the mentioned states, we sometimes try too hard and indulge in repetitive habits, both petty (e.g.listening to certain music), and those not to so much (e.g.alcohol, drugs). In any case, as human beings tend to generally rely on their analytic, thus categorizing powers, perhaps such systems would do us more damage than good if we cling to them in the times of our needs too much, too much being the key phrase. And regarding this topic this can be directly linked to the general dissonance between our rational and emotional abilities, where we deal much easier with the former, and usually are the slowest to develop the latter. So, advancing the "system" too much can perhaps latently mean promoting our rational part on the account of the emotional, or it happens to happen like that more often than we actually plan for, and because we don't live through these emotions if we should, but somehow postpone or cover them up. So that phrase: "Just let it go for a moment." while striking on the rational "order" and "clear classification" is letting ourselves just experience those emotions as they come, for us to afterward get to see how to deal with them. Afterward is in these moments essential here because the emotion is literally felt and we are clear enough from it to start the calming process where we can engage the mind more now, instead of a former suppression of emotions.
On the other hand, yes, it is possible to develop healthy coping mechanisms and we should doubtlessly do it. Psychotherapy and psychology are generally helpful with these, whereas we know an individual discovers those more pathological frameworks of dealing with whatever issues. Additionally, I will mention some ascetic practices. Apart from some far-eastern ones we usually have in mind, in many other monotheistic practices we encounter dealing with such problems, from the smallest of mood swings to larger imbalanced states of being. One example: among other such issues, Christian tradition recognizes something called a "Noonday demon":
"In the writings of Evagrius Ponticus, a Christian monk and ascetic, the Noonday Demon is specifically responsible for acedia, which he describes as "daemon qui etiam meridianus vocatur", attacking the cenobites most frequently between the hours of ten and two. It caused a sentiment characterized by exhaustion, listlessness, sadness, or dejection, restlessness, aversion to the cell and ascetic life, and yearning for family and former life." There are often instructions to engage in manual work and prayers which will empty the mind, where we notice "emptying the mind" as an ever-recurring momentum, which points exactly to, let's call them: the tricks our mind plays on us to engage us even further in the negative spiral.
It is a huge topic, but I hope I managed to convey the basics. :) Of course, we are not only "mind" and only "emotions", and we have to always remain aware these two are too intricately intertwined.
Also, perhaps at the first sight, I strayed a bit from the original question, asking about more daily moods. However, I think they are intersected with some more long-term states of mind, as we also form different coping/behavioral patterns along the way.