For some men, words are like coins spent freely at times of greatest need. Behavior is a much more reliable barometer of feelings than words.
Sex is a form of inebriation affecting speech and judgment.
If the feelings behind the words are lasting, the words will get repeated outside the bedroom. How and why we lie about love is, to some degree, a matter of gender. Women tend much more toward literary scrutiny and close textual analysis than men. Words show women where they stand in a relationship. They gather and hoard those words and phrases that are most redolent of romantic commitment.