Sexual contact is a human need.
The expression of emotion is a human need.
Sexual need is both physical and psychological.
The need to express emotion can take physical form.
Some sexual need is driven by deeper psychological factors, like the need to bolster self-esteem: the person who "sleeps around, " regardless of propriety or circumstance.
Needing to -- regardless of propriety or circumstance -- express one's feeling to others can be driven by the need to bolster self esteem, too: the person who simply has to say what he or she feels.
In both, there is catharsis of a kind (which is the valid reason for either engaging or expressing): having sex wipes away desire, for a while, at least. "Getting things off of one's chest" can make one feel better, for awhile.
But both approaches can be, depending on the individual, nothing more than a desperate attempt to prove one's worth to one's self (often at the expense of others).
In excess, both actions can erase future interpersonal paths.