Yup. Leave on time.
If you haven't already packed, then make a list and cross things off as you pack. That way you can refer to the list when you have a last minute panic of "have I packed X".
In your head, go through the journey and holiday and make sure you have everything for each stage:
How are you getting to the airport? Do you need tickets/a reservation/money to pay for transport?
At the airport: passports, tickets etc.
Separate out any liquids/gels that will need to be in a plastic bag to go through xray.
Anticipate anything else that will need to be separate - ipad/laptop/kindle etc.
Have you got chargers and adaptor plug(s)?
Do you know how to get to the hotel from the airport? Do you have means to pay transport
etc. etc.
Walk it though, and make sure you have everything.
My best mantra is to make sure I have things that cannot be bought (passports, tickets, bank card, phone, medicines, glasses) and then say to myself, that anything else can be bought so no need to panic.
Last of all, ENJOY it! Italy is a lovely country.