This is a common phenomenon. If you are new to traveling alone for more than a day or two at a time, and find solo travelers' depression or disorientation recurring with another trip or two, you may just decide solo travel is not for you, and instead could plan future travel with a companion or flexible tour groups. Some people just can't handle the sound of their own breathing for too long a time, because it forces them to look inward, and also heightens their ability to observe other disturbing things in the surrounding environment that you might not notice if chatting with a friend. Much as I enjoy traveling with others, I also enjoy my solo trips and the intensity of thought that they generate.
Things that help with the feelings of travelers depression, disorientation, loneliness:
1. Sign up for a city or excursionary small group sightseeing tour with a day or half-trip tour company based out of an American hotel. You'll meet English-speaking guides, and likely other Americans or English speakers you can chat with or share insights with in English, and sometimes even go to dinner with.
2. Plan in advance how you're going to get around (like how to ride the local Tokyo subway), especially if on a tight budget where you can't just hop a cab whenever you want (or there are no cabs) -- guidebooks with specific information, insiders tip books, FT, locations of American or English clubs or bars or hangouts for a break.
3. Carry a cell phone from home, or rent one there, if you need to make an emergency call (to home or your hotel), or if you just want to hear someone's voice instantly . Know how to use it in advance. Send/read lots of e-mail (including FT!).
4. Get lots of exercise and plenty of sleep, limit alcohol and mind-altering substances.
5. Keep a journal -- write down your observations and thoughts at the end of (or during) the day. Look around, there is always something interesting or a possible story behind a particular face or sight, or speculate what the story might be. Or write a little poem, it doesn't matter how bad you think it is. Find an English language bookstore (plan in advance) and hang out there, or go to English movies.
6. If nothing works, ask yourself why you're there in the first place. If it is to try and make your problems from home better by escaping to a distant land, you won't be successful. Go home and work on the problems.