I love this thread. It's so adventurous! Personally, I really encourage travelling alone, and I've done it myself several times over. I do wonder what the main purpose of your trip would be - reflection, or social hour? I really would urge you to not go with friends if you are set on having a trip for reflection. I met up with some friends in town when I went to Paris/London and it took away any amount of reflection I could have had, just due to distractions, despite having some alone time during the trip.
If you'd prefer to have a social trip and worried about safety, as someone posted the travel group tours for young adults are great - G adventures, Contiki tours, etc.
You could also easily go to any of the Carribean resorts - they are generally all pretty safe as long as you keep on the resort grounds and with the resort operated tours. It's also easy to make friends or have company on resorts.
If you're serious about reflection, definitely do not invite social time onto the trip. What I'd recommend for you to prepare is to start hanging out by yourself at home a few times to get used to it - perhaps you haven't done this before. Go to the bar, go to a restaurant by yourself. Eat, drink alone and enjoy your own company. Reflect. It takes some time getting used to, and the choice of restaurant/bar is important as well as the time of day you go.
Good luck!
*just saw that this is a super old thread as well, but I think this advice could help some still so I will leave it!