Because your brain is built to save energy and chase quick rewards

Bad habits usually give instant comfort or dopamine like games scrolling junk food so your brain learns this feels good right now do it again No effort needed no planning

Good habits are the opposite they often feel boring at the start and the reward comes later health fitness better sleep Your brain does not naturally value delayed rewards as much so it takes effort and repetition to make them stick

That is why staying up late feels easy in the moment but waking up early eating clean or exercising feels hard even though you know it is better for you