You have free will in your emotional development...
You are born with certain biochemical tendencies that affect your emotional state... but the brain is not merely biochemical- its is also topology of synapse.
And topology of synapse can be altered by thought alone.
It takes time and dedication to 'rewire' enough of your brain to significantly alter or compsensate for genetically determined biochemical responses... but it can be done.
You can eliminate anger, eliminate self centeredness, temper imeptuousness...
but doing so does require, at minimum the capacity to recognize these failings and honestly address them without rationalization.
But patience and perseverance is the key...
If you have 20 years practice wearing a certain pattern in your brain, expect it to take decades of steadfast effort to undo all of that programming.
You don't need drugs to deal with OCD if you have the intelligence and presence of mind to simply recognize you have that tendency and to consciously disallow yoursef to form habitual behaviors.
Meditation works...
And remember- be careful what you pretend to be, because you become the thing you pretend to be.
Pretend to be self aware, pretend to be mature, pretend that nothing upsets you....
And before long... you will find you are not pretending.