Set boundaries for you and your best friend
One of the most common reasons why best friends and significant others cannot work things out is because the significant other feels like the best friend is physically or emotionally too close or attached with their partner. This is a common problem for people who are fond of having platonic physical contact through simple gestures with their best friend, such as hugging or embracing. If this is the cause of the problem, the best thing that you can do is have a talk with your partner and set boundaries. Talk about the habits that you do, such as calling your best friend in the middle of the night, constantly hugging each other for no reason, or talking about each other’s body parts vulgarly.
Find common ground
This is one of the best ways to instill a positive relationship between two or more people since it gives them something positive to talk about. It is even highly advisable to find common ground, which can come in a form of a hobby that you may not be into yourself. This will give your best friend and your partner something that they can call their own. This may even pave the way for a deeper relationship, which will greatly benefit both your friendly and romantic relationships in the future.
Explain what they mean to you
If your partner and your best friend cannot seem to find common ground in anything or are still going at each other despite the set boundaries, have a long talk with each one of them. The focus of the conversation should not be centered on the actual problem. Instead, the conversation should be focused on what they mean to you. Explain to your partner that your best friend is like a brother or a sister to you and losing him or her would bring you a lot of pain. Explain to your best friend that you and your partner are serious about each other and that what you have is simply not a fling. By making these two solid points, your partner and your best friend will understand that making you choose between the two of them will bring you a lot of pain. They will also understand that they play an integral part in your life and that they cannot be replaced by someone else. This will help make them see that they need to get along for you.