It's a cliché, but a visit to the beach will make your day! With no tourists to crowd you out, Goa's beaches are serene and tranquil places to spend time with friends, especially in the evening once the sun is down.
Popular beaches like Baga and Anjuna still have activities happening regularly but it's places like Agonda, Candolim and Palolem that you really want to see if you're looking for a bit of privacy.
If you've been bitten by the shopping bug, then make sure to check out the local markets in these areas during the day. You'll get way better deals during this time and are free to haggle to your heart's content!