Form habits by starting with small, doable goals, for a short duration of time, such as two weeks. Mark off each day you successfully stick to your goal on a calendar. You can do this on a wall calendar, or there’s even an app designed especially for this called ‘Don’t Break The Chain!’. This very simple app was developed after psychological studies showed the long term success rate was increased if people can literally tick boxes for days they stick with their goals.
Your goal for two weeks might be to eat no refined sugar, or to eat raw vegetables as your afternoon snack (instead of a muffin!) everyday.
Stick with your daily goal everyday for two weeks consecutively and habits are being formed. Sure, you might not keep doing it every day forever more, but over time these habits will become an increasingly bigger part of your lifestyle.