Ask HN: Biggest life lessons for new-comers before entering into corporate world

I am asking this because I was working in a fin-tech startup having 800,000 active investors using the platform. No shortage of money and work. The work culture and work was really good , no office politics. I also worked on many feature and recently they launched a new product in which I was one of the core developer working on front-end. Everyone is happy with the product. The product manager, CEO, VP engineering, other company's team with which they have partnered with. And suddenly the CTO told me that we can't continue with you. I asked why? He says you have worked good in this project but 8 months ago you are not working as per company's expectation so we gave you overall rating on 2.5/5, so we decided we can't continue with you. But don't worry we'll try to search jobs for you.

I told that I was a fresher back then and this is my first company and this project is my first project in which I've worked as a team. He said there was no lack in your effort, learning new things, attitude towards the issue, and your coding skills, you will be a very good developer in 1 or 2 years. But we can't continue with you. Yes, you had came to me for reviews about your work. It was my mistake that I was not giving you proper review. Still we can't continue with you.

The lesson I've learned here is you can be fired at any time even after doing good work and improving yourself. It's good that I have learned this lesson quite early in my career(One year exp.) I want to know all other life lessons and suggestions from from more experienced folks