1. Before doing anything, figure it out firstly
Ask yourself if this is a decision you have already made with a clear mind, not an impulse decision. Maybe you have encountered a new adult friend finder with great potential. You feel that you don't have time to invest in two fwb partners at the same time, so you decide to give up the current one. You think you can give up everything for your new friend. But, before you do anything stupid, you need to understand that if you abandon your mature hookup partner, you are risking everything you have established.
What is your bottom line? Never put yourself in such a situation. Be very sure of your decision and make sure you don't regret it in time. Once you give up the friends with benefits relationship, you risk losing him forever. Even if he decides to return, things can become awkward, and you won't share the same bonds anymore. So you must stand firm and stick to your own.
2. Be candid and honest
Avoid saying that this is not your problem, it's my problem. This is a classic excuse after breaking up. Be honest and let him know why you decided to break up with him. Don't just disappear, and hope everything will go smoothly, you want it. Meet him politely, face-to-face, and let him understand it gently and easily. If that's not possible, a phone call or a text message will suffice. Be sure to explain the reason so that you can end it without leaving him indecisive.
3. Gradually reduce gender
Logically, neither of you should do too much preparation in the weeks before the adult affair dating relationship ends. Doing so could get him on a confusing journey and make things more complicated than they are now. Reduce the frequency of intimacy, this can be used as a prequel to break up. It's like a cushion to cushion the fall and make sure he won't get caught without knowing it. With less physical intimacy, it will irreversibly create an emotional distance between the two of you, making breakups easier to accept.
4. Express your words and intentions sincerely
Be sincere, and don't go too far if you don't want to. You have to admit that not everyone can maintain a casual friendship with those who have slept. Even if you can, he may not. So both of you must be very aware of this, and if one of you cannot become a normal friend, you will have to reach an agreement. If both of you are emotionally prepared and happy, then of course you can. Occasionally text each other, have a cup of coffee, or hang out together. Do what friends do. A true new friendship may come from this.