We use Agile/Scrum with Sprints. Each sprint is made up of the work that needs to be done for that sprint, basically a todo list. It gives you an end goal to work towards and a sense of accomplishment at the end of each sprint. One of the goals of the sprint is for the team to take on only the amount of work they can reasonably complete in the time given based on historic data and team input. It also makes it transparent to stakeholders what is being worked on and when it will be completed.
Quit. Poor or greedy managers are the diesease, this is the symptoms