Is it normal to feel less energetic at 25 than you did at 18?

I am only 25 but this year has really made me feel my age. I feel tired often and just less motivated then I have in the past. When I was 18…or even 20 for that matter I could jump up and ready for anything anytime any place. Lack of sleep, lack of food…whatever I was good to go. Now at 25 I feel like if I don’t have a full nights rest and a decent meal I am cranky or so tired I procrastinate to the point of dragging myself where I need to go or waiting til the last minute. Is this normal to feel such a drastic change? Is it just normal aging and getting older? Just curious what you guys have experienced.