I'm too old for this

I've been keeping up with my workouts and "upping" the weights...things are going good but....there are times when I struggle and just think to myself..."I'm too old for this". Again it's a matter of my brain being wayyyy younger than my body. I keep thinking that I can become the fit, thin girl I was (with a six pack) 4 years ago....it's too much damn work! But...I'll struggle on...I can at least get 1/2 way there...maybe 3/4...hell, who knows....I might just surprise myself!