you have to be in the right state of mind and stay in it. don’t get rid of every unhealthy snack all at once, it’ll be too hard and you’ll just want it more. slowly take away one at a time and replace it with a healthy alternative. personally i’ve replaced a lot of things like chips and cookies with fruit because fruit can come in multiples like chips :P try looking for different exercise routines too, there’s a perfect routine for everyone. and a size 8 is definitely not fat. i myself am a 6 in some stores, 8 in others and even a 4 sometimes. it totally depends on the store so don’t let the number get you down. 
i hope this helps!! good luck! xo