[annnnd]

I don't know enough about your situation, but you should know that A) managers are just people and make errors in judgements and B) sometimes managers exaggerate stuff like that to get more from employees (12h days for instance).

For A, you could pull a bunny out of a hat - finish a project early (as early as possible) and make sure it is noticed (but don't brag about it). For B - sometimes you have to compromise, and sometimes you don't have to. Can you find another job? Do you want to? Can you stand up to them? Depends on your situation...

Last but not least, "slow" is not the same as "not meeting the deadlines". Are you meeting them? Make sure this is noticed! I would rather have a "slow" member in my team who can reliably deliver good results in time than some "hotshot" who can delivers tons of (unusable) code in very fast time...

Bottom line: in companies what should matter is how much you contribute. Just make sure others notice it too.