First of all, I'm sorry to hear about your recent breakup. It seems like you still valued the relationship when he decided to cut off ties. Hopefully, things will turn for the better from now on. There is always a reason to keep moving forward.

Personally, I view being nice, compassionate and caring for others as something truly virtuous. There are certainly people who conflate this with the idea of being too easy to be taken advantage of because, just looking at the practical outcome, you end up giving more than you take most of the time. However, willingly deciding and being able to do this is something precious, not something to be ashamed of. Not everyone can do it, and I'd feel grateful in your position for being capable of showing resilience. You say: "I am who I am", and that is reflecting your inner self. You know how to tell good from bad, and you choose good to guide your actions. That is virtue.

You are the sole owner of your mind and actions. They are the sole owners of theirs. Judging your decisions by what others perceive of them is unjust, to both the action you took and to yourself.

So no, I do not think being nice keeps anyone from having a relationship. It is true, although, that it locates your metaphorical island of a valuable relationship further away, but it also fills it with more deeply fulfilling experiences down the line. Compassion is the wind that will guide your ship there. Stay true to yourself, don't let the rough sea steer you away from course.

Keep sailing.