People will always be doing things that you're not. You don't need to say "yes" to everything. Resist the temptation. You'll be happier.
Remember that Facebook personalities are carefully curated to portray particular images, with convenient omissions. For every happy photo posted, there are moments of sadness, loneliness and disappoint that don’t make it into your newsfeed.
The best way to cure your FOMO (fear of missing out) is to take a break (or sabbatical) from social media.
Instead of thinking about trips that you wish you had taken, spend time thinking about the next exciting adventure you want to go on.