Some great discussion on this topic, I hope Markena has found this useful. It is perfectly normal to have this fantasy. Some fantasies about meeting Brad Pitt or Julia Roberts, others fantasies about being beaten with crops. The world is full of variety and pretty much everybody fantasises on some level or another. Reading over the original post and what followed, I think Markena is asking if having this desire defines them as a person. Please correct me if I am wrong! The basic answer is no, we are not defined but what we fantasies about, they are an extension of ourselves.
To explore this idea further think about your favourite snack. You may think about eating it regularly, does this mean you are defined by your preference for an apple or biscuit? Of course not, and this works the same for our deepest, darkest fantasies. Wanting to express ourselves through sexual experiences and connections is very natural and the guilt that is being felt could be put down to something else. In my experience the guilt is more about our relationship with society and not the actual sex act we desire. The fact Markena enjoys humiliation is not what causes the guilt, it is the fact that Markena knows there could be others in society who might react negatively if they found out.
This is a normal response to thinking about our private lives being exposed in such a way. How bad would we feel if a spouse, sibling, work colleague or parent found out about our deepest fantasies? Society is not constructed for everyone to wear their private life on their sleeve. Hence why they are private. If I could give any advice or experience on this subject it would be to echo what others have said. Find a way to disconnect the fantasy from your everyday life. Spend time on a new hobby or go to social events perhaps. Realise that what we fantasies about is one small part of us mixed in with many other everyday parts. Everything has its place and time to be expressed. Working out when that is leads to a healthy relationship between our sex lives social lives
Another thing to try would be to explore the humiliation further. Does it have to revolve around Diapers? Can the diapers become a prop in a larger scene of humiliation? It could be that taking the diapers out and focusing on what it is about the humiliation one desires means the balance will be struck and then we can start to accept the fetish in a healthy way. Overall, we should never feel bad about our fantasies, they are good for us! We must learn to grow ourselves and be bigger than the fetish.