Lean In

Lean In, Expecting Good Things
Our perspective impacts how well we deal with the situation at hand. When we perceive the stakes to be high, we’re more likely to freeze—especially if we’re prone to perfectionism.
What does "Lean In" mean? In this part writer tries to make readers understand that sometimes unexpected things happen out of your plan so you have to accept it and be ready for it
Source: Don't overthink it by Anne Bogel

Lean In here means make a concerted effort, an extra effort, to dedicate yourself to the task at hand. Think of trying to open a door that is stuck - if you just half-heartedly push, the door may not budge. But if you really lean in and apply all your strength and force against the door, you have a much greater chance at success.

sobhan said:

What does "Lean In" mean? In this part writer tries to make readers understand that sometimes unexpected things happen out of your plan so you have to accept it and be ready for it

Yes, you've got it, Sobhan. She's saying that when something unexpected happens to disrupt our plans - difficult if we are prone to perfectionism - the key thing is to adapt, to adjust your plan to include the apparent anomaly. As you say, .

This is all clear from what she goes on to say: the best memories often start with something going wrong.

When spontaneity strikes (ha!), it’s helpful to purposefully adopt a low-stakes mindset. Instead of striving to choose the ideal option, we can aim to choose a good one, reminding ourselves that the best memories often start with something going wrong. And then, instead of resisting the change of plans, we can lean in, expecting good things.

I don't personally find the figure of leaning in, inclining oneself towards something, terribly helpful or vivid, but I'm clear that this is what she means.

It's a trendy phrase the last few years.

I believe it comes from this book.
Lean In - Wikipedia

Lean In: Women, Work, and the Will to Lead is a 2013 book written by Sheryl Sandberg, the chief operating officer of Facebook, and Nell Scovell, TV and magazine writer.

But there's also this:
https://www.washingtonpost.com/life...8-862a-b6a6f3ce8199_story.html?outputType=amp

The Lean In movement launched by Facebook Chief Operating Officer Sheryl Sandberg is officially over. Done. Fin.
Sandberg’s brand of self-empowerment feminism has endured waves of criticism ever since her 2013 best-selling book, “Lean In: Women, Work and the Will to Lead,” became a cultural phenomenon. But in the waning weeks of 2018 — ... — the potency of Sandberg’s individualistic, motivational mantra has fully eroded.