You could make it an explicit “either . . . or.”
I.e. “I think that people who are not made happier by having things either have the wrong things or have them incorrectly.”
I would go with “having things either have the wrong things or have them incorrectly.” Possibly keep the comma to match speech patterns / make it slightly clearer, though I think it looks better without it.
Would it help if I added an ellipsis between “having things” and “have the wrong things”?
You could make it an explicit “either . . . or.” I.e. “I think that people who are not made happier by having things either have the wrong things or have them incorrectly.”
Insert “tend to” after “having things”.
I would go with “having things either have the wrong things or have them incorrectly.” Possibly keep the comma to match speech patterns / make it slightly clearer, though I think it looks better without it.