Should you write your book in first, second or third person?

I (Matt) personally have written all of my books in first-person (I/me/my).

As long as you are sharing your own stories and advice/opinions in service of the reader (and always keep this in mind), it can be a great way of making your writing feel authentic.

If it feels right for you, definitely do it!

However, there's nothing wrong with using third-person (he/her/they/them) either. It's the most common way of doing things and works very well.

Second-person is uncommon, but can work great if it feels right to you (my favorite example of second person is How To Get Filthy Rich In Rising Asia).

By default, I recommend first-person for most Punchy Books (because most of us are writing from personal experience and our own advice/stories), but there's nothing wrong with other choices if you prefer them.