Some business people Plan Their Work & Work Their Plan. These people feel most comfortable when they have spent the time to plan before they act. These people feel confident because their plan-then-work approach to business has been successful. They expect there is a good chance success will repeat itself.

Other business people Take Each Day As It Comes. These people feel comfortable about their abilities and see no need to spend much time planning. These people feel confident because their day-by-day approach to business has been successful. They expect there is a good chance success will repeat itself.

There is one more group of business people: people who are not particularly comfortable or confident. They, for one reason or another, receive no particular forward-guidance or positive-direction from their past experiences. They feel, at best, acceptance of today's business-at-hand. Similarly, they feel, at best, acceptance of the fact they will experience tomorrow's business-at-hand. They feel no particular need to plan. They obtain no particular gratification from work actions.

Self-development experts and business gurus teach support Plan Your Work & Work Your Plan. 

I am not aware of any business guru who teaches Take Each Day As It Comes.

I have written a number of articles on this topic...for example, Strategic Planning - Why Bother!

I know, and am fascinated by, a very-successful business leader who favours Take Each Day As It Comes.

I learn everything I can about planning.

Here are a few things I have learned:

• Napoleon Hill may have been the first to write the phrase "Plan the Work and Work the Plan"...in his classic self-development bestseller 'Think and Grow Rich' (1937).
• Experts have identified 'Plan' as distinct activity linked to the pre-frontal cortex of the human brain....Executive BrainSmarts.
• Planning provides an opportunity to think through the possible scenarios and possible actions before they are performed...optimizing the use of talents and skills...and developing a mindset that understands we are not limited to accepting circumstances and situations, to a degree we can create circumstances and situations.
• There are many ways to approach planning: if you want to inject some creativity then I recommend Edward de Bono...for example, Six Thinking Hats

Footnote:

I just re-read Brain Tracy's 2003 book GOALS! [and I recommend this book]

In GOALS!, Brian Tracy provides the following answers to the question - Why Plan?

1. To Organize your thinking about the key issues.
2. To think through the Actions before you begin.
3. To allow thorough discussion in order to identify flaws and say What if?
4. To identify weaknesses
5. To identify Strengths and Opportunities
6. To focus time and money on those 1 or 2 vital things that are essential
7. To save Time, money, and Energy