I like what star-lover said, in relation to the fact that before that you have the Three of Swords, so that would mean that you have had to make a difficult decision, that would have been very tough on that person to make that decision, as that would involve heartbreak, but however painful that is, it is inevitable. I mean, in the Three of Swords you are basically getting to the heart of the matter, sort of like, I can stay where I am and feel battered and bruised for a lot longer, or I can move one, feel battered and bruised while I get over whatever I have to get over.
*I not meaning me personally*
So, the Four of Swords would be the time that you would need to just "be", go through the mourning process, have closure, even if it is only in your mind and your heart - meaning that you are not able to do it with the other person, or people, if related to a relationship. This time is the time for you, to pull yourself together, so to speak, and just feel the void. When the void is over, it could indicate when something new comes along, perhaps a new idea, as such. It is like being in limbo, or being at crossroads, during that time you are figuring out what you want, what you are about, and all of that. Sometimes when we are involved in certain relationships, or certain associations, or whatever, then sometimes we can lose our identity. Four of Swords can be the time that is needed to rediscover your identity.
As for it being negative, just might mean "not sure" LOL