Stimulus is the prerequisite of any action, it's the soul of efforts, fighting spirit, the thing making us strong enough to sustain and keep working even in highest adversities... some sort of stimulus is mandatory to sustain the urge to stay alive. Adversity on the other hand can be defined as lack of stimuli for growth, it's the scarcity of positive things, positive feelings, a threat to existence... The quantity and quality of adversities we face may be the results of our actions or may be purely matters of chance or maybe a combination of both... but they do come; the bad thing ends and the worse follows; surprises come one after another to the extent that you may stop getting surprised... typhoons come, tsunamis happen, earthquakes occur in your delicate mind and push you backwards sometimes far behind the starting line and you've to strive to reach to the starting line leave apart reaching the finishing line.
It requires a highly developed and strong frontal cortex for animals to think of the future and to keep on pressing the lever even if the food reward doesn't come for one time, two times, tens and hundreds of times... but what that poor frontal cortex shall do if thousands of presses are fruitless, and instead you start getting shocks..... I think frustration is a natural phenomenon if the situation is too frustrating. Frustration doesn't come alone; depression, aggression, decreased cognition are all it's companions. It's a vicious cycle, and it goes on affecting each and every part of our lives, making us a person we hardly would have imagined when we were not frustrated. Firstly we lose our voice and then our desire to have our own voice... the pen is there, so is the paper, but the collection of words is often soulless.
It requires intact cognition, lots of energy and high spirits to search meaning in meaningless tasks... it requires extreme confidence, passion and devotion to search traces of hopes in hopeless conditions. Sadly to frustrated tired brains even life saving tasks seem to be meaningless, slightly joyous tasks seem to be extremely mundane. Dullness, boredom, hopelessness, meaninglessness and also sadness... life gets soaked in such dark shades, we become adapted to them and eventually forget the sense of brightness. We come to a point where life can become extremely unproductive, highly dependent on the very scarce sources of stimulation it has... With all joys disappeared from it, the life can become synonymous to painful suffering.
But pain isn't a neutral thing... it's a stimulus. Frustration sensitizes us to all the little positive things we have in our lives, they all when combined are enough to make us to get up and start again with a different approach. It is painful of course, but pain is I feel a foundation of some sort of creative thinking... though this thinking is totally different from the creative thinking due to joy, it can be very productive. Even the act of imagining of how life would have been if things were slightly different is very soothing. Frustration is better than having no emotions at all, it doesn't feel good and thus can act as a stimulus to do something to get out of the situation... If compared to writing frustration isn't the end of the story, it's not a full stop nor is it a comma, it's writing the same sentences with a different tone and maybe with a different meaning... who knows if tomorrow something blissful happens and the next paragraph contains a tinge of smiling heaven in it.