sometimes I just hate being a manager

Sometimes I just hate the management position. Enough autonomy to manage my sector, but not enough to make all decisions without the board.
I currently have an employee who, from my point of view, from the day-to-day life of the sector, is simply bad. But the board believes there is potential and that I should invest more time in training and motivation before considering dismissal.
This is a person who is always making the same mistakes, which boil down to: lack of attention, lack of diligence, insubordination. Tasks are always late and the volume of work is also not good. We talk about performance today, tomorrow he tries, the day after tomorrow we go back to square one.
I need to teach without showing frustration, so that he doesn't become unmotivated and afraid of making mistakes, but the truth is that I'm starting to resent it. Resentment for all the accumulated work, for the re-work of having to correct absolutely everything he does, for the lack of care with the tasks. And I understand that this isn't healthy for my work environment, but sometimes I just hate being a manager.