You can't just "decide to master faster than light travel" because it's probably not possible. See, as far as we can tell right now, any two of the following can coexist (but not all three): faster than light travel, relativity and causality. Relativity has been experimentally verified to the best of our ability and hasn't come up wrong yet, and if causality can be broken you can get all sorts of weird shenanigans and paradoxes happening. That's not to say it's 100% impossible that there are ways around that, but it's nothing I'd bet the farm on...