Look at this sentence: You can’t come in unless you have a membership card. This sentence means “the only way for you to come in is to have a card.” Unless is not simply “if not”. It kinda means “only if” Or this one: your new credit card won’t work unless you validate it through your bank profile. Which means when you receive your new credit card, it won’t be operative immediately; the only way to get it to work is to go to your profile and finish the validation procedure. In your examples you should use: You’d be happier if you didn’t have such high expectations. Your second example makes little sense to me... could you explain it better?

The first one is type 2 conditional so I'd re-write it like : you would be happier if you had such high expectations. ( Although this sentence sounds kinda weird in terms of conceptual meaning .. it must be: if you didn't have ) "Unless " doesn't make sense here. you use " Unless " to make a simple exception. for example: I'm NOT gonna give you the password unless you give me yours I'm NOT gonna give you my password if you don't give me yours.