Can't Maintain Good Habits

Yesterday I was thinking about the fact I am unable to maintain any basic healthy habits for extended periods of time.  I get on healthy kicks for days/weeks/month at a time and then forget all about it.  One example of this is taking vitamins.  Earlier this year I made it a point to take a vitamin everyday.  I even got to the point where I purchased the vitamin packs with 7 pills in each to help support my overall health due to diabetes.  I haven't taken a vitamin in at least 2 months now.  Another example of starting and stopping healthy habits is exercise.  The month leading into the Halloween party I was all about exercise.  I started working out at least 15 minutes a day for 4 or 5 days a week trying to get toned for the party.  I haven't lifted a weight, did a push up or sit up since the week before the party.  Good news is I am small framed so it does not take much effort for me to shape up to how I like to look.  As I sit here with a bottle of water in my hand, I think about another failed healthy habit.  I always go back and forth with drinking water.  In the last 4 hours, I have consumed 2 bottled waters.  I probably won't drink anymore water for at least a week.  I don't know why I can't maintain healthy habits.