There are two things you should protect at all costs, because once damaged, they are difficult to restore.
1) Your HEALTH. You are given ONE body (by your creator), you are given stewardship over it, and you need to make it last. Unfortunately, you are also given cravings and impulses that are in constant conflict with maintaining a healthy body. I am a forty-something woman who weighs about the same now as when I was in college. I wore a bikini last summer, and didn't embarass my family when doing so. One of my top priorities in life is to make it as long and fulfilling as possible, and I cannot do that without pristine health. There are a few things that are out of our control, healthwise, but most factors are controllable. Caffeine, tobacco, alcohol, sugar (high fructose corn syrup especially), chemicals (pesticides, aspartame, sucralose, chlorine, etc), processed food, driving habits, eating habits, activity level , stress level, spirituality are all things we can choose to control which have a profound impact on our health. Excuses are little comfort for the family of a person who has died too young. You cannot enjoy everything life has to offer if you are consumed with health problems. Being healthy is also CHEAPER, leaving more disposable income for investment or other enjoyments in life.
2) Your REPUTATION. When jobs are in short supply, and job seekers are plentiful, you can certainly make yourself desirable if you have maintained a good reputation. There are many aspects to this: honesty, work ethic, promptness, reliability, attention to detail, quality of work, creativity, motivation, etc. You do not need to excel in every single area, but if you excel in none you give an employer no reason to choose you over someone else who does excel. Reputation is also paramount in personal matters. You don't want to be the person no one ever believes, or no one can count on, or no one will lend to. You are also an example to others, especially children and grandchildren if you have them. If your life were a book, with nothing glossed over or left out, would you want your family to read it? Write the book you are proud to have people read.
These two things that I protect dearly have made my life very fulfilling.