Well it could be several things, like if the two people are incompatible or simply you're expectations are too high, idealizing romance to always be a place of happiness.
It seems to me that you really would like to have one, but you need to really work on yourself, like learning that you can control your actions despite your mood. Just because you're upset doesn't give you the right to yell, or be cruel or spiteful for example (not saying you do this). And also recognizing that your partner isn't there to satisfy your every little whim as that is pretty selfish, even your mother isn't responsible for that. Not only that, but it's endlessly exhausting trying to satisfy someone who makes you feel constantly short of their expectations. It's not fair to them. It's not just about finding a partner who meets your entire checklist and what they can provide for you. One must also question themselves. Are they ready for a relationship? What do YOU contribute to the relationship? What can you do to make things better in terms of relationships, but also for you to live a happy, satisfied life? And when things don't go according to plan, as they sometimes do, whether it was preventable or not, you have the ability to change things around and still have fun at the end of the night with your sweetie ^^.
Hopefully I'm not coming off as harsh as I'm not trying to attack you. I think it's a great place to take your experience into a learning experience. Analyze it, and develop from it.