It takes 2 weeks to form and break habits. If you can't make 14 days then you really need to have a hard look at yourself and if you are really trying.

80% of relapse back into chronic behavior happens within the first year.

So basically.

>First Week
>First Two Weeks
>First Month
>First Year

Those are the hurdles to get over. Things also improve and also get tougher after each hurdle.