There's many clichés to describe it, including "if you are not winning then you are losing", if you not getting stronger - then you are getting weaker and too many other similar examples too numerous to mention.
The main issue here is that the only guarantee in life is change - nothing stays the same.
Even the hardest granite is undergoing the process of change.
Forget about death and taxes, there is nothing certain about either of those two issues with proper financial management and the new genetic sciences and technologies rapidly approaching our reality.
But change is a most definite guarantee in life - and the only two real possibilities are up and down, stronger or weaker, bigger or smaller.
This is important to know when it comes to your health, because your life is either in a negative routine cycle of degeneration, or it is in a positive routine cycle of regeneration and both are directly related to your testosterone level - which is very much within your domain to control.
If you incrementally increase the physical stresses on your body each day, it will keep your brain in the mode of producing increased amounts of testosterone each day, and this increase in testosterone will feedback into increased motivation and being more active and busy in your life.
Your new found energy will be noticed by other people who will more attracted to your positive energy as much as they are more attracted by your physical body.
This is the process of making sure than your guaranteed change is a positive and pleasurable one that extends your life, fulfills your happiness expectations and extends your life.
Fail to invest in the slight increase in your level of physical exertion each day, and your change rate will be a downward spiral into being even more obese, more lethargic, and less pleasant to be around.