In the case of most cards in tarot, unless the position of the card tells you otherwise, the card will represent one of your actions. That is not the case with the 7 of swords. It is always someone else, unless the position of the card doesn't specifically point out that you are the 7 of swords.
The card means that you will encounter someone that is trying to lie to you, or to manipulate you in some way, and you might also realize that. It can appear in a love relationship also, when the other person is just trying to manipulate you into thinking they are interested in you. But the influence might suggest that the other person pretends in order to extract some kind of information from you or to get you to reveal fact about you or another person. The card is therefore also connected to spying as Waite also pointed out.
But sometimes the person in the 7 of swords will just say something to make you feel good so that he/she doesn't hurt you. Then this card is more a card of diplomacy.