23 hours after I wrote the first post, I felt very tough to continue a new activity. I remembered the book that I read entitled "How to master your habits". That book explains that you can't change your habits because it's automatically done by humans. 90% of human do whatever in their life unconsciously. Therefore, there's no way to change a habit. It only can be replaced by a new habit.
Changing a habit is not easy, you must make a new activity and consist at it around 30 days. After that the new habits formed, and the past habit will disapeared. It is a lesson or hikmah of fasting in ramadhan. Allah want to reset the human both physically and mentally for 30 days. So, human will be back to fitrah when ramadhan finish and meets Eid el-fitr. It is also one of the reason why the name of celebrated day after ramadhon is Eid el-fitr.