Narcissism is arrested emotional development, at the emotional age of about two years old (which is the healthy narcissistic developmental stage). Parental permissiveness or disinterest allows a child to avoid growing past the 'terrible twos' to develop a sense of empathy, responsibility and socialization. Society's focus on youth worship also aids this lack of development, and all the social media, reality TV shows and focus on "it's all about me" completes the job.
A romantic relationship -- with the partner whom you hope and expect will provide you with love, joy and fulfillment of your dreams -- that turns into a miserable and disappointing failure is a very painful experience. I'm sorry you had to go through this.
I hope you will be suspicious if a future date seems "too good to be true" -- and observe him carefully to see if he has good character or not. Ask about previous relationships, friendships, and family. A man who is disconnected from other people is probably not emotionally available.
Know the signs of emotional blackmail:
1. A demand. Your guy won't take "no" for an answer, and requests are really demands.
2. Resistance. When every discussion turns into an argument.
3. Pressure. He pressures you to go along.
4. Threats. He uses threatening or coercing tactics: threatening to end the relationship, intense persuading, rage, badgering.
"How to Keep Yourself Out of a Violent Relationship" will help you know what to look for.
The Unofficial Guide to Dating Again has the information you need to date wisely and successfully.