My biggest fear was being able to accomplish all of the things I wanted to or be able to have enough time to really understand the culture. There is a balance you have to find when you travel abroad. A balance in how much you travel and how much you settle into the culture you are in, as well as a balance of whether to go to the touristy places or off the beaten path.
I would first make a list of places you really want to see or goals you want to achieve (Google reviews and pictures help a ton to deem if something is important, but make sure to read more than just one or two to get a real idea). It is tiring to be on the go-go-go, so do not burn yourself out trying to go everywhere and see everything, the world is big, try to prioritize on what you REALLY want to do. With that being said, some of those things you want to see will be the big tourist attractions; that is because they really are great! But be aware of when you go for crowds or booking tours in advance. To climb the dome in the Duomo in Florence, book in advance! Hostelworld.com is a great way to find hostels, and of course, airbnb.com is an awesome tool for apartments. Cinque Terre, Venice, Lucca, and Lake Como are truly incredible! I also would look into booking a villa in the hills of Italy. We found a fantastic one in Garfangana that was very cheap with a pool! It was very gorgeous. Also, the beaches in Pietrasanta are wonderful!
With all of that being said, I realized that having the correct mindset for what you want to accomplish is key. I realized that you can not control everything, and you have to be able to go with the flow, and if you have an inkling to do something, there is a reason you have it - follow that!
You will not be able to do EVERYTHING on your list, but to enjoy each day is much more important. Traveling alone to a new country where you do not know the language takes an adjustment, try to get the tears or nerves out of the way as quickly as you can, to treat each day as a gift - it goes fast!