I have indulged in these fantasies many times - it's not unusual to think about hypothetical futures and it's especially not uncommon to come up with stories about those hypothetical futures. It's even more common for you to be the main character of these hypotheticals. It's never been compulsory, I often have to stop my mind from wandering and these thoughts are no different from any others. Fantasies like these are essentially nothing more than a fanfiction of the real world.

What's more important is how you analyze these thoughts and what you feel about having them. If they are actually concerning to you and you are worried about controlling these types of fantasies, go to your doctor and get some referrals for therapy or counseling - many scams exist that specifically target men for especially this type of psych stuff, so try to stick to professional channels whenever possible.