When I hit my 30's (I'm 35 now), my body started changing; again. The last time I morphed so significantly was puberty. I noticed my total invincibility and immortality being called into question after hard bike rides, or rock climbs. I thought "what!?!?," what everyone's been saying is true; your body's effectiveness starts to decline with age? Hangovers became real when I hit 30. Prior to that they were a farce as far as I was concerned. I've spent the past few years focusing on a few areas to determine they're overall impact on my well-being. A couple of them are obvious, but are often taken for granted and therefore usually ignored. I thought I'd share my experience with aging in this phase.
As a child I used to get severe headaches. After many medical evaluations, no-one could come up with a resolution. On my own, I established a connection between my headaches and water consumption. Too little water, yielded headaches. Enough water, and I was fine. I've found my overall health is directly connected to my water intake. If I find myself with a cold, or the flu, its severity, or very existence, is purely a function of how much, or little, water I'd been drinking. The lesson here has been simply to drink a few glasses of plain 'ol water everyday. When I drink a lot of water everyday, I feel great. When I don't, I feel tired, and dragged down.
For a few years in a row, I wound up with a chronic, non-productive, dry cough that would last months on end. Again, medical evaluation yielded nothing. I thought I'd try taking a multi-vitamin as just a random attempt at changing my body's chemistry. I've been taking a men's formulated multi-vitamin for a few years now, and the cough abated the very year I started. Furthermore, my body feels much more balanced now.
If I don't regularly exercise (as in a few times per week of something) my life goes to hell. I get sick, I wind up with low energy, I gain weight, I get depressed, I get cranky, I get irrational, I get impatient. The time I invest in exercise is a drop in the bucket with respect to overall productivity when I don't exercise.
I've found that if I keep these three things in check, my life is great. If I don't, things go south.