Changing my goals

I did some stretches for my stomach, which is good.  There was even a plan put into place.  One extra minute per five minute stretch per week until I get to exercise for about 30 minutes per day.  I saw my shadow this morning I didn't like what I saw.  It brought to mind that even though my goal of at least 10-15 minutes per day is temporary, I realize that I need to push myself harder.  The goal that I was given this morning is realistic enough and I admit that I do procrastinate.  I hope that I don't make too many excuses if any at all.  I walk for 10-15 minutes per day but I "tap out" within five minutes.  Maybe I should incorporate stretches or some other exercises into my routine.  That would be helpful.  I admit I am out of shape and I look and "feel" out of shape so starting off slow is a good thing but how often should I change my goals?