[AaronStar]

Whilst I believe our emotions are mostly spontaneous, there are also triggers behind it linked to our personality.
For example, a sensitive person that often feels lonely and needs company to feel happy, will become sad if they go to the cinema alone.
Therefore, the emotion is not really controlled but there is an explicable trigger behind it.
With some practice of various kinds people may try to obtain some control over these triggers, the same way that therapeutic sessions work.
For different individuals the approach may be unique, such as meditation or over-exposure to the trigger, or contemplation over the issue to come to peace with it. Sadly, in many cases people may not be able to achieve such control so easily.
Exactly due to the reason that sometimes triggers tend to be provoked by essential and unalterable parts of us, this is why we say that emotions just happen.
For a super merciful person, the vision of slaughtering a chicken cannot simply become desensitized.
Maybe it is that deep inside, we like who we are, even if we do not like the exact result at times.
I wouldn't change my own sensitivity because I like myself exactly because I have deeper appreciation of thins. So, even if I get sad easily, I do not want it exactly to change. Maybe to eradicate the most toxic and useless triggers and preserve the ones that make me proud of myself. Therefore, I don't want to stop mourning for chickens, even if it makes me feel sad. But I would like to stop overthinking about the next working day.
So maybe it is mostly about finding an own method to control the toxic tendencies but sometimes it may be so difficult to accomplish it!
Life lessons and life situations do often change us in a certain direction but is the process controllable or does it happen naturally? Particular situations hit a certain chord and the emitted note builds the result as an independent process. You don't really decide how your thought will alter your face mimics, but you can contemplate yourself, practice intent, observe the result and control the direction. Usually you will like the result of a correct intent, just as you'd like the result of fitness efforts.
Of course we don't really decide how to react essentially, just as we cannot control the vital force behind hair growth.
But just as we can use hair products to accelerate the hair growth, it may be useful to observe and keep track of what is going on in our lives, observe the current lesson life is trying to teach us and take at least SOME action.
Finding the meaning of life and working on bettering ourselves comes hand by hand.
Whatever determines the direction of this process is entirely based on fundamental beliefs, personal traits, life values and understanding of the universe.