Though the form of your loyalty is subject to change, real loyalty is a choice and it starts from within. Loyalty is a moral commitment which can only be made when you value the relationship enough. Loyalty is one of my basic principles and if this is true for you, then you shall not backstab a person who considered you to be a friend, nor will you not start a friendship just for personal gain.
If loyalty is one of your principles, that means that if you’re not loyal to your friends, you’re not loyal to yourself. Betraying a friend would be breaking your principles and therefore becomes betraying yourself. If you are strong, committed and for real with it, you won’t let this happen.
When you consider loyalty a priority you will notice you won’t make as much “friends” because you and others know that when you get into it; you commit to it.