I feel that just like good clothes, each case has to be
individually studied and custom-made. If there was a single answer
to this (or any other question concerning human characters and
emotions), than life would be too simple and uninteresting,
wouldn't it?
Some guys want a one-night-stand and make no efforts to cover it
up. They talk about sex and mean it.
Some guys want a one-night-stand and will take the pains to cover
it up. They may not talk a lot about sex, but the motive is there.
They may go by indirect means - eg. use love to get sex.
Some guys want a short-term sexual relationship and make no efforts
to cover it up. They talk a lot about sex, mean it....and will
continue with the relationship, but will break off after a short
period.
Some guys want a short-term sexual relationship and will cover it
up. They may not talk a lot about sex, but may use love or
attraction and sweet words to get it. The ulterior motive is
there.....and the result is the same. After some time, they will
break up.
Some guys are sincere about a relationship. However, after the
first sex, they may feel that there is a character clash or sexual
incompatibility. So they may distance themselves.
In the above examples, I've used the words "guys" and "sex". More
accurately, the words "people" and "objectives" should be
used.
