In every relationship there exists the Love. Love does not mean Love relationship between lovers. Relationship between any two persons has three stages TRUST, LOVE, RESPONSIBILITY. With the beginning of any relation trust forms the base of the relationship. With development of the Trust it makes them to believe on each other. With passage of time this trust slowly develops into love. When they are in love with each other the relationship is perfect. To have this perfect relationship till after the last breathe a big word Responsibility comes. Love is incomplete without responsibility. As simple as this fourteen-letter word sound it is as difficult to accomplish.
Now the relation is established between two persons. Every relationship has love and the love is always accompanied by expectation. It’s true if you love someone you will definitely have more or less but some expectations from your lovesome. More is love higher are expectations. When we are not able to come up to the expectation that is the thing which affects the love between them and ultimately the relationship.
As an engineer I would define it in a better way, Expectation and Love are directly proportional to each other and breaking up of a relation is inversely proportional to not satisfying the expectation of your love some.
In short more you love someone more is the expectation and greater efforts you have to make to sustain the relationship for life time.