I've said it before, I'll say it again, and I'll keep saying it until you do it. "What are you waiting for? Go!"
Excuse #1 - I don't like to go places by myself
When your definition of "solo travel" is going to the grocery store, work, and then home, I can understand why you wouldn't like to go places by yourself. Your solo travel experience is limited to places that don't allow for much exploration or spark of imagination. If you don't like to go places by yourself, dig into why. For most people I talk to, they feel conspicuous being alone. The next time you go out with one or more friends, I want you to count the number of times you look around the room and think - "oh, look at that poor person over there, all alone." Do you do it? I am guessing the answer is a big, fat "NO". Take small steps. Venture out locally to a spa and a restaurant. Take a book or a journal when you go out. Be absorbed in what you're doing. Or take a big, floppy hat and huge sunglasses and focus on acting mysterious and generating the "who's that?" buzz! It's a kick. Give it a try.
Excuse #2 - I can't spend that kind of money on myself
Sure, if you're on a goal plan to have all your debt paid off, don't rip out your credit cards and charge your way to Istanbul. Be smart about it. Even on a financial plan, you need to set aside a few dollars for leisure. Even if you're squirreling away $25 a week, in no time you have enough money for a good local excursion - by plane, train, or automobile. However, to get back to the original excuse of not spending money on you - here's my question back. When you're rested, at peace, and feel balanced, do you act and react with more peace and balance to people and situations in your life? Being the best version of you requires that you spend time with you. In some cases, that means spending money, getting some "you time" in, and restoring your balance.
Excuse #3 - I can't leave my dog, bird, plant, pet rock, etc.
Because there is NO ONE on the planet who could possibly help out? Get over yourself. Ask for help.
Excuse #4 - Flying to, driving, and generally moving around in any town that I don't know stresses me out.
I'm not advocating anything that would cause you to have a panic attack. Work within your own psyche. Take small steps again (see #1). Go to a small local town near you and act like a tourist. Stop at the first gas station and ask where the best breakfast in town is served. Then, when you're at that cute cafe or coffee shop, ask what's fun to do that's nearby. Go to a National Monument that's close. Some of my most entertaining conversations are with the folks that work and volunteer at those sites. Of course, that usually generates the next excuse:
Excuse #5 - I'm too shy to do any of this.
When you go somewhere that no one knows you, you can be anyone you want to be (see #2 and the floppy hat). Get out of your own head! Sure, you'll encounter people who may not want to have a conversation, but trust me, they are few and far between. Try it!
As much as I travel, even though it is mostly for work, I still take each solo trip as a new adventure. In some cases, my travels only take me between the airport, my hotel room, and the office, but even on those trips, I still find that I learn something new, see something different, or find a new way of looking at the world. If you don't take any travel advice from anyone else this year - take this to heart: go have an adventure.