- too much frantic hyperactivity for too long

- too short deadlines so you have to dip into 'personal' energy to meet them in time

- too much concurrent spillover of past work and getting new/constantly shifting objectives so past work always remains pending completion

- greater responsibility but less flexibility in approach

- difficulty in estimation of date of task completion, so as more time passes, more dread of looming intense future work to make up for pace

see how much any of these contribute to how you feel