As is well known, a new year resolution is highly regarded by Hashem. It shows that a person is serious. The trick is to choose something one will keep. Even if it is very small it is significant if it is stuck too because then it becomes part of life. Small and steady.
A person should really be in touch with themselves and know what they need to work on. Ill tell you what I am doing, I decided that instead of taking on new things, Ill take things I already do and do them better. Basically try to fine tune my Davening, Brochos, learning….
Just take one area you know you need to improve on and really work on it and improve. It has to be something you work on steadily and consistently otherwise dont expect any change. Also pick something important like Brochos with kavana….or at least asher yatzar with kavanah… Dont pick anything that you know you wont be able to stick with.