There are resolutions to change of all sorts, but the ones to DO something are far the easiest. If you are going to read more books or eat better, you get a thousand chances a day to put that into motion. Stop for a few minutes before heading off to work to read a chapter, read a little more before dinner and a little more before bedtime. Add some carrots to your lunchtime meal of a sandwich. Park father away and walk more. Clean a closet or a corner of a room and you are on the way to success. Take the steps. Do, do, do, take action, and so it is easy to score on the "do something" resolutions.
But giving something up is an entirely different matter. If you are going to stop eating salty things or stop drinking caffeinated beverages or quit smoking or give up a drug or cease a gambling habit or stop watching television or end your nail biting, you have a thousand thousand times a day to get it wrong. Even if you forego the morning coffee for a nice orange juice, the pot is still brewing when you get to work and even if you refuse to give in then, there are the multiple offers by the waiter at lunch and the drive past a half dozen Starbucks and Caribou's on the way to everywhere and the coffeemaker on the counter top when you get home. If you manage to get into the shower without that first cigarette, there is the drive to work and those poor souls smoking by the back door that would be glad to share one with you for the sake of your company and each time one of your friends takes a break and invites you along and the after lunch smoke you have to resist and at some point, you are sitting at your desk and every minute is one more minute you have to say no to getting up and going out for a smoke.
If you do that one in a thousand chances at the good thing, you have succeeded in your positive "do something" resolution, but you have to say no a thousand times each day to succeed in your "stop something" resolution and one of one thousand where you give in counts as failure for that day.
Making a "do something" change is a walk in the park compared to making a "quit something" change. And after a few days, the new "doing" starts to kick in as habit, but if you crave the thing you are quitting 10 fewer times each day, it is a hundred days before you have a single crave free day and even then, there are countless triggers in the world to pull you back.
The force of habit is an easy thing to make and a terrible hard long long road to break.