If you're connected to 500 people and each person has 2-3 days a year that are "lifefaker" worthy... then it's pretty obvious how you'd feel left out. Each day you'll see 5 amazing posts that make you feel like you're living a terrible life. This is pretty standard stuff. It's standard by young people to not share sad things or things that won't fetch a lot of likes or envy. It's common to post things that aren't even happening now or recently but to share moments from the past that were great even if your life is pretty crap at the moment. It's about creating the image that your life is fantastic even if it really isn't.