You can only be in one place at any moment in time. If you feel you are missing out on something then you are. But it’s not the party, or being with another person that you’re missing, it’s your own life.
As long as you are thinking of where you could be, you are marking yourself absent from where you are now. Which means you are nowhere.
Many people spend their entire life in ‘nowhere’, would it not be better to “Mind The Gap” and be Now Here!