I think you are very close to explanation. Ideas in human minds can be presented as facts. If you decide that you are happy by some setting - that becomes a fact to you, while in reality that is a belief. The same about depression and sadness - you can get impacted by information you did not knew and would not be impacted if you were in blissful ignorance and some people choose exactly that choice. Some people get psychosis and their mind is hallucinating that they are on fire - that is real to them as what are your experiences, though those also are not based on facts, but serve as an information delivery to your brain.

The whole issue with human minds is that it is not built to deal with scientific facts, but with socium of other people. You can't use facts when operating with society - you have to use symbols, that they will associate with. And I think that the issue is with you(as it is my experience as well) - I can guarantee, that there are people, that will explain to your family members EXACTLY the same ideas, that you are trying to explain to them... and they will agree to that person - and not to you, because you are clearly doing it wrong.