Have a tendency to exaggerate / lose his/her temper / make snap (quick) decisions

To pop the question
To "pop the question" means to ask someone to marry you. 

To tie the knot
To "tie the knot" means to get married.

To be on the rocks
To be "on the rocks" means to be having an unpleasant time in a romantic relationship because you are not getting along.

To make up
To "make up" means to forgive someone after an argument so that you both feel better and are no longer angry at each other.

To play hard to get
To "play hard to get" means to act as if you are not interested in someone so that they will try harder to get you to be interested in them.

Fall for
To "fall for" someone means to begin to have romantic feelings for that person.

Fall in love
To "fall in love" means to begin to feel loving feelings for that person.

Be attracted to
To "be attracted to" someone means that you have romantic feelings for them.

Be compatible
To "be compatible" with someone means that it is easy for you to get along with them and that you enjoy spending time with each other.

Have a lot in common
To "have a lot in common" means that you have a lot of the same interests and hobbies as another person and so you find it easy to talk to them.

Be interested in
To "be interested in" someone means that you have romantic feelings for them and you would like to know them better.

Engaged
To be "engaged" to someone means that you have agreed to marry them but have not yet married them.

To propose
To propose means to ask someone to marry you.

To stand someone up
If you "stand someone up," it means that you had a date planned with them but you did not show up or tell them that you were not going to show up.

Married
To be married means that you are in a permanent romantic relationship with someone.

Single
To be single means that you are not married.

To get divorced
To get divorced means to end your marriage.