I'm getting near 30 years old. It sure doesn't feel like it. My mind feels as sharp—no—actually more sharper than it's ever been. I'm more aware of who I am, what's going on, where I at, why I'm doing it, and how I'm going to do it, than I've ever been before. Maybe that's wisdom talking, or it's hubris; I leave it to the reader to decide that one.
Bodywise, I feel like I'm probably been in the best shape I've every been as well. That does come with some caveats however. My body is definitely slowing down, that's for sure. I don't feel it too often, because I've always caried myself about the same, using my body more for endurance than peak output. However, I've noticed the changes in my metabolism. I'm certainly not the drinker I used to be too. The weekend at Purdue a few weeks ago was great, but these days a night of heavy drinking will put me down for a day or so. Not that I really miss it though. I'd prefer my balance of smart/somewhat heavy drinking without getting stupid/forgetful drunk over heavy drinking; it's a better balance.
Getting back over to the world of the mind, I've noticed over the last few years I've been really able to really focus my thoughts to pinpoint percission. This has been incredibly helpful since I've taken on my various computer-related jobs (web, software developer, etc.) over the last few years. Especially since working with modern computers, inherently multitasking machine these days, can be as distracting as it is productive. There's been a ton of news out there about how the brain isn't built for multitasking and it just makes us perform each task worse. Let's call it the mental equivalent of being a jack of all trades, master of none(thanks Wikipedia for more obscure knowledge!).
When dealing with computers, the more complex computer systems you have, the more chances occur for something to screw up. This also means while you try to fix things, you have more chances you'll be presented with false leads and dead ends. Thus, making all the more important you don't get distracted or lead off path with superfluous, or irrelevant, details. In order to achieve this hyper-focal thinking, I often have to mentally shut off my senses where I'm completely enveloped in one feeling, that of thought.
In this state, I try to jack into (I'm not one for cliche cyperpunk phrases but this is the best thing that comes to mind to describe it) the mind of the computer to understand what's going on, using a kind of theory of the mind for the computer brain. You see, computers are completely linear, left brain, thinking machines. While the complexities of computers make it seem, at face value, that they don't operate that way, but they do. Each action a computer takes is the result of some series of instructions, a script, an algorithm. If you can see the script, or source code, you can figure out what the computer is doing. This however is complicated by modern computers that have many different instructions going on in different places. You have to figure out what which scripts are interacting with which. It's not an easy task; it's near immpossible for the brain to conceptualize everything running on a modern computer at once, the best you can hope for is to minimize interactions and isolate different parts that are relevant to each so that you can gain insight on what's going on.
As useful and intersting as this sort of hyper-focal thinking is, I think it puts a toll on me. Not in the sense that it wears me out; mental exhaustion isn't something I feel too often unlike physical exhaustion. It's more about the consequences of thinking one particular way. It disorts my thinking, like I'm thinking in only in one dimension with the left side of my brain. That probably isn't completely true, but it feels like it sometimes. I don't think I'm a very fun person to be around when I'm in that perspective. I don't joke as much, I stick to whatever task I have at hand, and tend not to focus on the bigger picture. I could on about this particular topic, but I'm going to put it down for now. There's a lot of ideas & thoughts I've been sitting on for some time that is related to this. I'll revisit it sometime later.