Aiming for a size 8

Today I bought a pair of size 8 Tall 515 Levis.  At almost 5' 10", my goal is to fit them.  SO, to make sure I have the motivation, I ripped off the tags so I can't take them back.  I don't want to waste good money now, do I?  At slightly less than 180, I am currently in a 12 comfortably and I can button the 10 and the 8 but they both come with large muffin tops that should not be seen in public.  The last time I wore an 8, I was 18 or 19 years old so that's about 15 years ago, before having 3 kids.  My weight goal right now is 160, about a 50 pound loss all total, but I am technically going to go until the 8s fit well which I believe is somewhere around 155.