Determine that you are no longer interested in dating or spending time with the individual. Reflect on the details of your fling. After all, this is a person you have spent time with and you're now familiar with each other. Be sure that you are ready to stop seeing the person and that you want to move on without further contact. Ending a fling and then returning for more can result in hurt feelings and confusion.
Invite your partner to meet at a convenient time and place where you'll have privacy. Tell your partner clearly and respectfully that you have decided that you should not see each other anymore. If she wants to know why it's appropriate to offer a reason, but be honest and do make excuses. If you're no longer interested or you have met someone else, simply be as honest as possible without being rude. Try to conclude on a positive note with the intention of being respectful and clear about the break.
Refrain from further contact. While you may spend some weekend nights alone at home in the absence of your fling partner, it's important to stick with your decision to end the relationship. If he calls or sends messages, refrain from answering and don't give in to a temptation to contact him. It is all too probable that rekindling a fling will bring things to an unhappy end the second time around if one partner begins to develop feelings for the other or feels she is being used for a casual physical relationship.
Reflect on your fling. Consider what you enjoyed about your partner and the experiences you had together. This process will help you develop a stronger understanding of what you really want from a serious relationship. Reflecting also helps you know whether you're ready to pursue serious dating or if you want to continue to date casually.