A hard thing I find in these situations is when people try to coerce you emotionally. "This a very critical job. Deadline is nearing. You can get anything you need". I find it very tough to refuse in such a scenario.
Perhaps take your own emotions into account, and weigh them against what you're being asked to do? Abstractly: If I do A I'll feel good about A, but terrible about B. If I don't do A I'll feel bad about A, but fantastic about B. Pick the one that's most important to "you".
