In your career, you will be frustrated at times.
Things won't always work the way you think. They're not as neat as your textbook examples. Not as orderly as you might assume - even at large, reputable organizations. The inner workings tend to be messier.
You entered your field to make an impact. But what makes sense isn't always what is done. The best solution isn't always applied. The smartest person isn't always in charge. Logic doesn't always prevail.
There are times when your ideas will be dismissed. Your recommendations will be ignored. Your intellect will be questioned, and your patience will be tried.
Sometimes you must do things that make little sense - to jump through hoops to comply with policy. Or go through the motions to follow precedence. Or do a song and dance to placate the powers that be.
You will especially be vexed by people. Not everyone pulls their own weight. Not everyone cares about the mission. Not everyone wants to see you succeed. It's not unlike your group projects in school.
So if you want to change the way things are done, be prepared to meet resistance and indifference. Don't be discouraged. But do approach your work with a sober mind.
You cannot change everything all at once. In some contexts, you will need time to prove yourself. In others, you won't be able to effect major change - ever.
What then should you do when faced with frustrations?
To borrow from the popular serenity prayer, take your situation as it is, not as you'd have it. Your job will not perfectly fulfill you - that's too high a standard. But you can seek to be "reasonably happy."
For what you can change, pursue with courage and resolve. For what you cannot, find peace in the silver linings. To know the difference, cultivate wisdom and humility. Take it one day at a time.