Edit: Less flippantly, with age comes some benefits. Yeah, while I had a lot of energy in my younger years and could eat whatever I damned well pleased, as much as I damned well pleased, my attitudes of that time period, which were very much born of my inexperience, had some long term costs I am still paying for. But the tradeoff is that with those lessons, I can make better judgements on what actions contribute or detract from longer-term goals, or even what longer-term goals might be worth having.
If you play your cards right, getting older can be a good thing. So rather than thinking of being old as some terrible thing to be avoided at all costs, look to see how it could be played to your advantage. Come 30, what things would be fulfilling to be doing or having? If your answer is "nothing", then I think I can justly accuse you of not even trying to look.