I'm happy today

Today I feel so happy because I insisted on my exercise today, although I'm still very far from my  the goal is very far away from . But I'm sure that one day, I will be very happy ~ I will be thin.

[Basically good.  I tried to change the phrase so to what you meant.  Don't exercise to thin - exercise to be healthy.  Being the right weight (rather than being thin) will take care of itself.  I've met  several models casually, and almost all of them were constantly unhappy about their weight and the way they looked.  Food was an enemy rather than an enjoyment.  Yes, you should maintain a healthy weight, but don't use the women in the magazines as your ideal - you will just make yourself unhappy.  Sorry for the rant.]

I'm happy today

Today I feel so happy because I insistED on DOING my exerciseS today(.) Although the goal is very far away, I insisted that one day, WILL BE very happy ~ I will be thin.