Like it or not, you have to share the people you love with other people! So loosen the grip you currently have on your best friend or partner. Give them more space to explore other aspects of their social life. You bring a lot of value to their life and can be confident in that — so why worry that they are spending time with someone else? If you get too possessive about your relationship, you send a message that the assurance you need is more important that the other person's independence.