If it was me, and assuming you are either <30 because you are still in school, or in a professional school (legal, MD, Dentist, etc), then I'd say that your goal is two-fold.

1) put as much as 80% into long-term growth funds - this is for whenever you retire. Now, those type funds depending on risk tend to run between 6% and 12% which means in either 12 years or 6 years you could double your money. If 12%, you would double your money TWICE. so $400K becomes $800K and then $1.6MM.

So, if you are 28, at 40, you have a tidy sum, at 52, you should able to retire if you want, your money should have increase over those 24 years to nearly $3.2MM, and depending on the monthly expenses you've grown accustomed to, and any debt you've take on instead of staying debt free, you'll be able to spend about $100,000 a year and last nearly 36 years on that alone, tossing in a decent history for SSN and you should be able to supplement that at 70, and stretch it to 40-45 years.

2) the balance use as your 'reserve' fund to purchase little things that come along and use cash as your strong point for those things. Contribute to this and a retirement fund. Then use only your cash whenever possible.

Remember, living within your means also means not deciding a 10,000 sq ft home is a NECESSITY unless you have 12 kids. I see a lot of people with huge homes and huge mortgages that are just unreal for 3-5 person families.

Buy used cars. I've had TWO new cars in 60 years. I used both until they were 20 years old. every other vehicle was purchased second hand, and I've owned over 30 vehicles.