As I've written elsewhere on this blog, emotions can be seen as the framework within and from which thoughts arise and assert themselves.
That is to say, sad emotions give rise to sad thoughts, angry emotions give rise to angry thoughts and neutral emotions give rise to neutral thoughts.
If it is a good idea to keep one's thoughts in good order, then this especially applies to one's emotional dispositions, since the quality and intensity of our emotions determine the quality and intensity of our thoughts.
In my writing Consequences of Worldview I wrote the following:
[I]t is advisable to keep one's thoughts in good order so as to be spared the throes of emotional turbulence - thoughts and emotions being mutually reinforcing though not identical agents - and its potential negative consequences for one's actions.
This raises a question: if emotions are the framework and context within and from which thoughts occur, what is the impact of thoughts on the emotions?
This is a pressing question when there is so much noise at the moment about the importance of positive thinking so as to counter negative emotionality.
My view is that emotions hold sway over thoughts in that, for example, in a state of deep sadness triggered by an event it is very hard to think in a happy way.
That being said good thought hygiene which avoids extremes, rumination, obsession and self-bullying - in others words, that aims at some form of neutrality if not jauntiness - will have a positive effect on one's emotions since it is clinically proven that thoughts have an impact on the quality of our emotions provided one is not already prey to an emotional state.
One thing that cognitive behavioural therapy helped me the most with - with regards to the clinical depression I used to suffer from - was to teach me how to correct and steer the thoughts that arose from my depressed state. The therapy entailed working with the thoughts as triggered by depressed states in order to make them reach a happier outcome and judgement (including on myself) than in their initial, un-edited state which tended towards self-denigration.
As one self-help author puts it, is is helpful to watch the thinker in us, i.e. to think about one's thinking in such a way as to be aware of the thoughts that pop into our head and monitor/edit them so as to spare ourselves stressful and therefore vulnerable emotional reactions through the agency of the cortisol hormone produced by the adrenal gland.
However, emotions are often triggered outside any conscious and deliberate thought pattern, particularly those of a sudden nature, which is why in such cases I recommend fully accepting the emotion rather than fighting it but still attempt to maintain, to as high a degree as possible, some free-will agency and editing power towards the content of the thoughts the sudden emotion gives rise to.
In other words, it can be helpful, in as far as possible, to be an external witness to emotions and the thoughts they produce in ourselves - particularly when negative and stress-inducing - so as not to overly identify with said emotions and thoughts. Thus, I recommend allowing them their (hopefully) ephemeral say whilst not taking them too seriously or giving them more than their due as the objective, final truth.