Because you got too comfortable with being secretive and detached.
You love having your own independent life, which is an awesome mentality – but you haven’t yet realized that being in a relationship doesn’t mean you can’t also be independent. You spent too much time in 2017 trying to keep a safe distance from whoever you were seeing or dating or talking to you, and you caught so caught up in trying to keep your personal life and your dating life separate that it just ended up blowing up in your face. You need to spend 2018 learning how to let people in while still maintaining a healthy balance of individuality – it’s absolutely possible.
Because you actually put too much logic and practicality into your dating life.
Being practical, reasonable, and rational in love is actually important – to a point. But you were so practical, and so set on being logical that you started looking at love too formulaically. Rather than allowing yourself to just breathe and live in the moment and enjoy the person you were with, you were trying to plan out every step – are we compatible? at what point would we want to move in together? at what age would they want to start a family? At some point, you do have to answer these kinds of questions when you possibly want to form a life with someone, but it becomes a problem when it takes up every second of your time together and is the only thing you think about. You should continue to be smart and well-reasoned in your love life, but you also have to live a little.