I have worked under both good and bad managers, run my own shop and have been around the block a few times as well. :) One of the things I've learned over time is the power of a gantt chart. Sometimes the manager is also learning and the use of a tool like the gantt chart often provides an opportunity for both of you to reach an 'agreement of expectations'. If the gantt chart is reasonably accurate and the time necessary to complete the task is within reason, then the manager - having had regard to the gantt chart and knowing the constraints should be able to 'ease off a bit'... hopefully. But the point is, that you should consider breaking down each big task into smaller tasks and using a gantt chart 'map it out'. Provided each of you can reach a reasonable 'set of expectations' it can be dealt with. The gantt chart is of course only a tool 'used to find mutual expectations of delivery', there are other tools. Hope this helps.
M Hamilton