Teresa Giudice's Day 1 ... So Lonely

Teresa Giudice has a ton of lonely nights and days ahead, and kicked off her ME time with a pensive, solo walk.

The 'Real Housewives' star took the stroll Thursday near her home in NJ ... no doubt, thinking about the next 3 plus years. Hubby, Joe Giudice, shipped off to prison on Wednesday to begin his 41 month sentence.

It won't be a walk in the park for her, and definitely NOT for Joe.