When people think of being discouraged they usually think of a person who doesn't have to want to complete the task
I don't want to finish this paper.
If someone says someone is defeated they usually mean they are 'beat' or have no want to do something. This word does not show any form of aggravation, merely a form of unwant .
Yeah, I'm good. I'll just drive home. Who likes mountain climbing anyway?
This person looks to be frustrated. They are at their peak of self doubt and inability to work. When You think of a frustrated person you see someone so outraged by a task they are unable to do said task or any other.
Determined has a positive connotation, because we tend to think someone who is determined will work harder, do better, and have more passion for what they are doing.
I know the answer to this question
Motivated makes us think of a person with a drive or passion to do something, but may not succeed. If a person is motivated they are less likely to complete/do well on a task. Therefore this word doesn't quite have a positive connotation.
I made it to the top of this mountain!
We don't wish to be called a megalomaniac, because it refers to a person who is so obsessed with themselves and their power. They are overly power-hungry.