As I thought about this, it was easier to understand in terms of our survival instinct. In primitive times, if you were kicked out by your tribe, you were probably going to die. So, if you are scrolling social media and find that a group of your friends got together without you, your brain tells you "My tribe is kicking me out! Be afraid! Be very afraid!"
I remember seven years ago when a woman I had dated some was telling me that she didn't have anyone. She lamented that she didn't have any friends around. (This attitude was, paradoxically, self-perpetuating.) I told her that I felt the same way often. I was broke and trying to find my way through that. I didn't feel like I could date anyone seriously until I was in a better place financially. She commented that she had seen on my Facebook page that I had gone to dinner with some friends. She was jealous. I don't think it was romantic jealousy at that point. She just wanted to go to dinner with some friends and didn't feel like she had anyone to do that with. That was deeply painful for her.
We all have an innate need to belong. For those without a partner, that need can feel deeply painful. I have a few thoughts for any of you who have experienced pain over this issue.
If you are an introvert, I know it can feel difficult to reach out and you may be fearful of rejection, even in platonic relationships. Face your fear and do it. Make a circle of friends for yourself. Include people from various different parts of your personal history. Have several different circles of friends. I have many friends that I still keep in touch with from high school, my mission, college, and other places I have lived. Some of them live near and some far. My faith and my friends were the two things that sustained me most in the crucible of divorce. For those who do it all alone, I honestly don't know how you do it. But, recognize that you don't have to do it alone. Many of my old friends had not communicated with me in many years when I reached out to them as my divorce was ongoing. In virtually every case, it was as if no time had passed. They were all loving and welcoming.
The fear of rejection can be even scarier in dating than in platonic relationships. However, even when I was not ready to get married again, casual dating helped very much to meet my social needs. I was honest with the women I dated (especially and including Cathy) about my situation and said I would not be ready for something leading to marriage for a while. My dates tended to be relatively inexpensive because of my situation at the time. But I had no shortage of them and I made some good friends that way.
In every area of our lives that really matters, we believe in being intentional--except for relationships. In that area, we seem to want it to just happen by magic. We believe in setting goals in our careers, in managing and growing our money, in church service and callings, in our educational pursuits and whatever else we may be doing. But we often take a very different approach when it comes to relationships, both romantic and platonic. We take the approach that "If it happens it happens." That is not how it happens. If you are feeling lonely or jealous because of things you've seen on social media or otherwise, be intentional about broadening your circle and having plenty of people who are willing to have fun with you. You can do this with a little intentional effort. For example, you could set the intention at the beginning of the week to call two old friends before the end of the week to catch up.
I really counsel against putting a lot of dating photos on social media before you are exclusive with someone. Assume that everyone you go on a date with has some level of interest in you. It could be hurtful to them to see you with someone else. I am not suggesting that you should be deceitful and pretend to be exclusive when you are not. Be honest with your partners about where you are in terms of commitment. But even if they know you are dating other people, it may still feel painful for them to see pictures of you having fun with another partner. I don't think you need to adopt this kind of approach with platonic friendships. However, be cognizant of who might feel left out. Consider inviting them. If there is some reason you can't, maybe don't throw it in their face. Use your privacy settings.
Are any of those painful judgments true? Not really. They are your thoughts and stories. They come from your insecurities and not from anyone else's conduct. So it is important to begin by understanding that jealous and painful feelings when it comes to friends and social media are not truly coming from social media. The feelings are coming from inside ourselves. Once we understand that, we can adopt a different thought about the situation. "That friend values me for deep and serious conversation, and perhaps values these other friends for lighthearted fun." That's a much less heavy thought right? Perhaps you could think, "I'm glad those two are having fun together. They probably really needed to get out and do that." Being happy for them and sharing in their joy is a lot more fun than being jealous and miserable. Perhaps you could adopt the thought, "That looks like fun. I ought to call a friend and make plans to do the same thing." Now you are acting and not being acted upon. You are controlling your thoughts instead of letting your thoughts control you.