discontent
A feeling of unhappiness because things are not good enough.
Discontent is a feeling of dissatisfaction or unhappiness with your current situation. When you feel discontent, something about your circumstances bothers you enough that you can't quite settle down and feel satisfied, even if nothing is terribly wrong.
A student might feel discontent with always getting B grades when they want to earn A's. A basketball player might feel discontent sitting on the bench, wanting more playing time. Workers might experience discontent with unfair pay or poor working conditions. The feeling often pushes people to make changes: the student studies harder, the player practices more, and the workers ask for improvements.
Discontent sits between mild disappointment and serious misery. It's that nagging, persistent sense that things could and should be better, strong enough to stay with you over time.
History shows that discontent can drive progress. Many important changes started because people felt discontent with injustice or inefficiency and worked to improve things. But discontent can also make someone perpetually unsatisfied, always wanting more without appreciating what they have.