Live for the moment in that sense is too modernistic and simplified. I'd say view that advice in it's deeper, maybe twisted meaning which is "Live your day to it's fullest" not "Just live your day"
The difference between the two is the first is more Freudian, Live today like it's the only day that matters. Live today like today is the only day you can make an impact on your life, like today is the last day you can get a degree, ask out the girl you want to talk to, make a lifestyle change, take a hike. Too many people live like they have endless time, just look at gamer culture which is about "grinding for the next unlockable" because they've fallen for faux achievements that riddle their mind with dopamine and leave nothing behind. It's why twitch and the idea of streamer culture is so cancerous, "play video games 5 hours a day and talk to yourself 4 days a week if you want a chance to be famous"
The second version of it is a more hedonistic approach which leads towards instant unhappiness like you mentioned. Consider the idea people push forward of "not being a slave to religion because of how restrictive it is" or "freeing yourself of society's expectations of you and doing what you want". In reality, anytime you do that you trade one master for another since without some longterm purpose or moral compass you become a slave to pleasure.
I'd say give yourself a longterm goal and pursue it today. Reevaluate your daily time investments and cut out those that are unfulfilling or detrimental to your own personal health. Pursue something worth. Go the Jordan Peterson route, clean your room, take responsibility, etc.
My first step was to delete all the pictures off of my phone besides personal ones because I was stock piling memes and pornography, try going nofap, limit my screen time, start amore dedicated and extensive daily hygiene routine, and become more active in my life with cooking and physical exercise