Once you're in a relationship, it's already defined, if what you're in doesn't seem defined it's not a relationship, it's something else. In relationships there are constants and variables, most times girls get blinded by the fact that they are in love, and forget to notice that exact time the guy stops loving, and vice versa.... There's a particular time when your partner feels full of you and wants to exit, there's a time when you need to notice that you are becoming stale, that's the time to change, girls need to be dynamic, you know... It involves little things, from changing hairstyle to Changing your routine of cloths, it involves changing from over caring and over pampering to creating adventures and putting him in some suspense, it involves switching from been cheerful all the time to pretending to need his support or emotional help.... If you have a static relationship, defined or undefined you will surely be heart broken ..... Let your relationship be dynamic... Quit all the routines.... He or she will get tired....
Reasons for heartbreaks which I stated out base on what I think and Experiences are....
Inability to define the relationship from the beginning.......
A young man may enter a relationship without the intention of marriage, while the lady involved in such hook, may be thinking and concluding marriage. If this is not well defined from the beginning, with time when the obvious will be irresistible, there is bound to be an heartbreak. The same goes to the ladies, a lady may decides to go into a relationship just for protection, to have someone to keep her comfortable for the moment or to pay her bills without necessarily having mind of marriage, while the young man involved may be concluding in his mind yes I have found my missing rib. Suddenly he proposes and she said no "let just be friends ". This is very absurd and may trigger actions(suicidal).