Argument from Adverse Consequences

This fallacy occurs when negative results would occur if the opposition were correct. 

Often, this is used as a defense mechanism. 

Conversely, the opposite (when positive results occur if the arguer is correct) is equally fallacious.

This fallacy is closely related to argumentum ad hominem and argumentum ad misrecordiam.

Example: 

The water technician said that test results for my well water just came back positive for lethal amounts of the poison arsenic. If this is true, my entire family has been drinking arsenic-laced water since the chemical spill yesterday, and we are all going to die in the next few hours. The water technician is obviously wrong because I don't want myself or my family to die.

Example: 

My boyfriend said that he had to work at the office late, but when I called his office phone, a co-worker answered it and said he hadn't been at work all day.

I don't want to believe that my boyfriend lied to me because it would break my heart, and I could no longer trust him. Therefore, he did not lie to me.