Twin Flames engage in the divine mission which is the purpose they are in existence in the first place. In order to engage in this mission, the soul beings merge into one on all levels: 3D physical level, 4D spiritual level and 5D at the highest level, soul source. The mission combines with the missions of other twin flames in union as a collective which raises the universal vibration which results in universal unconditional love, peace and healing. The romantic aspect of the twin flame union is a by product of the divine mission.
There's plenty of souls out there who, for whatever reason, think being a twin flame is the soulmate style du jour. That's simply not the case. For a whole soul being seeking to be a twin flame, the mission of the twin flame or twin flames journey to union will seem difficult. You can't put a square peg into a round hole. Soulmates are focused on all the exciting things romance has to offer while twin flames are more focused on their mission. Romance does exist between twin flames however it comes as a by product of the divine mission.
There's a journey twins embark on to achieve union on all levels and a basic template for that journey exists. Half of the time twins don't even realize they're on the journey for being so engrossed in their path. And, in their mission.