Day One at a new company - who will you be here? What will your work say about you?
Not that you can’t be the same person you were yesterday - that person got you hired after all. But how will you be more of who you are? The best version of what you can be?
Remember, as of Day One, everyone that meets you begins their relationship with you HERE. You define the reputation you will come to be known by, for good or bad.
Everything you are today - all your learning, your blunders, your hard conversations, success, failures and learning - all this is combined to be the mature professional you are today. You should have taken this new job for a good reason, now be sure you seek to live that opportunity.
Spend a few minutes considering how you want to present yourself, given that you effectively have a clean slate with which to work.