The live for today mentally always results in regret.

It's extremely stressful and taxing physically (yes, and yes, I did mean physically), mentally, and emotionally [and extremely rewarding under the right conditions].

Although the mentality is their addition projects are worth way more than what is the perceived worth.

I have a hard time mentally processing how this will lead to much higher rents.

Seems like you are referring to the FIRE mentality. 

How does one get past the idea of NOT having a traditional retirement account and into the mentality of leaning on rentals to consistently bring in cash flow?

The velocity of deals being done can make  a difference in market cycles at various points in time.Buying assets with top market rents and high debt could be a bad thing as it saddles you with non-producing with loss or neutral debt load which can hurt ability by more properties.I saw in the last downturn of 2007,2008 where people had a buy anything mentality and the train stopped.

You need to buy some kitchen equipment, one or two of the good basic cookbooks like "The Joy of Cooking" or Bittman's "How to Cook Everything," and build a sustainable repertoire of 10-15 cheap, healthy dinners with a few variations each that you can put together easily and quickly.Better for your pocket, better for your mental health because it will help ground you, better for your love life because smart, capable people appreciate personal cooking skills in others.The top three expenses of the American household, as @Scott Trench's book taught me, are housing, transportation, and food.

But I think it's important to mentally prepare yourself for some of the obstacles you will most likely face.

You are now well equipped, at least, mentally, to jump in.