Imagine sitting at a shitty job, going to the bathroom, and browsing instagram... hey look, here's Alice eating at a fancy restaurant.. here's Bob on a beach... here's Cecilia at a party... here's Doug moutain climbing... and you're stuck at a shitty job.
Instagram doesn't show eg. Bob working for months to save up for a trip to a shitty seaside location, hotel with bedbugs, overpriced cocktails and a sewage flowing into the sea just out of the visible part in the photo... but you don't see any of the bad stuff, just other people having fun, and you having to deal with all the bad stuff. Add all the filters, and all other people are pretty, have nice skin, look skinny.. and you look like shit after 7 hours on the job and one more to go.