When is it ok?

When is it ok to accept imperfection from yourself on this journey to health and when should you expect more?  I'm struggling with this tonight. 

A little background...I'm doing the WW Walk Challenge.  They give you a training plan to help you prepare for a 5K.  I started with week 2 because week 1 had walking times that were lower than what I was already doing.  So, week 2...you are supposed to do this:
Sun-15 min
Mon-18 min
Tues-Rest
Wed - 18 min
Thurs - 20 min
Fri - Rest
Sat - 20 min

So, I had stayed right on track through today.  Here was my after work schedule today-

Pick up Baby S from daycare, rush home for an appointment at the house.  Immediately after the appt I went into the kitchen to throw together dinner and eat.  Immediately after eating (even dishes got put on hold) we needed to run to Target for some must-haves for Andy and Baby S.  Back home to feed Baby S and play with her for 30 minutes while her food settled on her belly.  Then it was time to put her to bed.  We are in the process of trying to teach her how to fall asleep on her own and if you've ever done such a thing...it is incredibly stressful.  So, by the time we finished that I was an extremely tense ball of nerves and it was already 8:40..and until I have a baby who sleeps through the night I like to aim for a 9:30 bedtime.  So, I had less than an hour before bed and I still had to make bottles and get things together for the next day.  Luckily Andy had already finished dishes and washed bottles or else I would have felt completely overwhelmed.  I had an internal debate for a few minutes about whether or not I wanted to do my 20 minutes for my WW walk.  I convinced myself to do it.  I got in my workout clothes and hopped on the treadmill.  About 4 minutes in I wanted to quit.  I pushed myself and tried all of my tricks to get through it.  I imagined all of the women I've been following in the blogosphere who are doing so amazingly well and who talk about how wonderful it feels to be lighter.  I tried reminding myself how bad I want that.  I tried visualizing myself next summer with Baby S who will then be a toddler.  I tried to visualize running with her and swimming with her at a much healthier weight.  But time seemed to take longer and longer.  I just wanted to quit.  Finally, at 10 minutes...I did.

So, now my heart is torn.  There is a part of me who thinks I should just be proud of myself for even getting on the treadmill after such a tough night.  But there's another, louder part of me who is really disappointed in myself for quitting.  I keep asking myself "how do you expect to succeed at this if you quit?" 

The thing is...I do believe that we have to learn to be forgiving and understanding of ourselves to get through this journey.  But, how do you know when you've gone from being forgiving of yourself to making excuses for yourself?  I really want to be successful at this for the first time in my life.  And I know that finding the balance between these two emotions is going to be imperative.  I'm just not sure where to start on finding that balance.