I'm no expert on the subject, but it seems to me that the only people who are 'incapable' of feeling or receiving love are those who are commited to staying that way. If you're open to it, then it can and most likely will happen.

If you're just striving to care about others and be likeable... I don't know how to answer that, because I have a feeling that there is a context to your question but I don't know what it is. It would be great if you could elaborate on that part of your question.

How do you know you love somebody? There are a lot of answers to that, but none of them are precise or can be applied to all situations. My feelings for my husband are just as intense now as they were when I first started dating him more than 6 years ago. I think the only difference is that he isn't on my mind 24/7 now (ie, infatuation). But I care about every feeling he has and with each decision I make in my own life, I consider how it would impact him. To me, that's how I know that I love him.

Good luck with your quest!