For me, it was an incredibly difficult time to adjust. I'm selfish with my time, I need me time, I need creative thinking - and it went away.
It's easy to become a shadow of your former self trying to be the best father. My advice is, find balance. Find time for yourself, make time for your partner. She will need that time alone too.
Your job as a father, during the first year, is to make sure the baby survives. That's it. Don't think you'll always be able to make it stop crying, or think you can attend to its every need. You'll be lucky if you can put it to sleep. The first year is rough, baby wants mum, a lot. You're the supporting actor, you won't be the lead act. It will feel unfair, that no matter how hard you try, you can't deliver.
Finally, know that the first 6 months are the hardest. It gets easier, and the 2nd year is easier than the first, etc. Don't lose yourself and be patient, compassionate, and understand: life won't be your life anymore. It's about the family's and it hurts, but it's so much deeper and so much more interesting. This will be the biggest growth you'll ever accomplish as an adult, becoming a father.
So enjoy the best of it (they grow up so fast), and brush off the bad parts. Embrace dad jokes and becoming that dad, because humour is the best weapon to the loss of your personal life.
Good luck, all the best.