For example, Brim points out victims of sexual assault don't have feelings of attachment for their abusers nor can having regular sex in an unhappy marriage "fix" the relationship or make you fall in love again. While sex can deepen an existing bond between two people, the thing that makes us feel attached is the "intimacy of the experience and the innate chemistry of the partners," she says. World globe An icon of the world globe, indicating different international options. It's only natural we associate those good feelings with the person we shared them with and we are left wanting more of them. Like most things in life, there is no instant formula for having feelings for someone — with or without having sex. We asked a few experts who let us know the real reason you may be feeling more attached, attracted or "in love" with someone after you've had a sexual interaction. But what is happening in our brains when we are physical with another person that causes this shift?