Dear Marek Libelt:
My answer: self care in the context of a relationship means:
1. Evaluate who the person with whom you are developing a relationship and proceed with the relationship only if that person is respectful to you at all times, meaning never abusive. And if the two of you, often enough, express empathy toward each other.
2. Be assertive within the relationship, make your reasonable needs and wants known to the other person. Negotiate when needed so that the relationship serves both parties, and so, that it is a Win-Win relationship.
anita