It's no surprise that lovers don't last long on Game of Thrones, especially if those loves are powerful and happy and stand to lose more than they could possibly gain. However, as Season 6's final episode aired Sunday night, even the most devoted of viewers were left wondering, "Why did Daenerys break up with Daarios on Game of Thrones?"
Their relationship has lasted longer than most, which is saying something, but when Daenerys set her sights on Westeros, she realized that one of her strongest assets is (sadly) her sexuality. If she wants to build alliances, in a patriarchal world that values women only so long as they please the men around them and produce sons, her availability to wed is a political bargaining chip. Marriage is the ultimate unifier, and if Daenerys finds herself in need of an ally only marriage can give her, she needs to be free to make that alliance a reality. She can't do that if Daarios is in the picture, by her side as a lover and someone others will see as a threat.
In other words, Daenerys broke up with Daarios because it made the most sense, it will definitely keep her safe, and it will ensure that she has the best chance at becoming the ruler of all the seven kingdoms. In other words, Daenerys has her priorities, and a man-friend isn't one of hem. I mean, if that's not a reason to break up with someone, I don't know what is.