Retirement Planner: Go with the flow when it comes to stock market

With American stocks reaching an historic high water mark last week, the feeling I now have reminds me of the days when I was the parent of teenage children. 
A recent study said that more than 70,000 Americans are over 100 years old and that one-third of them were still driving. What those folks represent is the statistical "long tail" of the bell curve that represents how long the average male and female will live beyond 65.  
Everything I read on the subject tells me that the most anyone can safely expect to take as income from their retirement accounts is 4 percent per year.  
Find ways to save money so you can take advantage of this year's $18,000 maximum limit ($24,000 for those 50 or over.) Remember that you're only affluent and not rich. The rich are different. They have money.  
At best, economists and money managers offer food for thought in interviews or written opinions, but beyond their entertainment value, these "insights" have little bearing on the basics that matter to amateur investors.  
The goal in retirement is to organize investments in such a way that they generate income of roughly 5 percent per year and still gain in value overall to keep pace with inflation. This is not that difficult.  
Let transportation services like Uber and Lyft do the driving.  
"Time is money" is a common cliché in a business context, but that refers to the cost of wasted time. Time instead of money describes a situation in which time is a replacement for money -- a more positive slant on the subject.  
Confusion tends to reign when markets hit record highs. Advisers and brokers trying to be helpful feel compelled to suggest "taking profits" largely to demonstrate that they (advisers and brokers) are being useful. Investors are tempted to act on the advice, remembering how sorry they have been in the past when the market tanked and they later regretted that they weren't sitting on cash to buy back in. Dream on.  
How can a young person new to the workforce be convinced that setting some earnings aside is worth whatever pleasure they might otherwise gain from indulging in poor spending habits -- spending money on just stuff?