If you find yourself constantly disappointed or hurt in relationships, take a look at your dating history. Chances are, the people in your past all have something in common that's leading to the less-than-fulfilling relationships you've had with them.
Sit down and make a list. Write down the names of all your partners, how long you dated, what attracted you to them initially, what you liked about the relationship, what you didn't, how you felt at different stages of the relationship, and finally, why it ended. Yes, this might be a painful trip down memory lane, but it's important to figure out what didn't work in your past to know how to move forward with purpose.
Don't leave anything out. Be honest with yourself (no one else is going to see this list, so there's no need to omit something).
Now look at the list. Notice if there are any patterns. For example, maybe you're attracted to needy partners, which means you end up taking on most of the relationship responsibilities. You make all the plans, you initiate conversations, you always pick the restaurants, you lose yourself in fulfilling the needs of your partner. And after a few months, it gets exhausting, it's not sustainable, but your partners don't see a problem and so it ends.
Don't do anything with this information right away, but keep it in mind as you start dating. Now you know what you've been attracted to in the past, and also what hasn't worked. You have the information and power to stay away from the same patterns that have led to unfulfilling relationships in the past.