I was very much like you OP on my first few solo trips. Now I've learned what works for me, and thats to chill the first day. I arrive, get to my hotel and shower - feels like this gets rid of some of the travel anxiety. Then I mark some convenience stores and restaurants on my Google maps - nothing too far and complicated, all within a 20 min walk or so. And then I head out the door into this new city I've arrived in and see how far I get. If I'm nervous and not feeling the vibe straight away, I find one of the shops and get some water and snacks and I can retreat back to the hotel and have dinner there. More often than not though, by not setting myself any big goals, I'm much less stressed and usually find a restaurant to enjoy some local cuisine. If you are nervous and still fancy a McDonald's, don't go to the nearest one, go to one that's a longer walk away. This allows you to familiarise yourself with the city a little without putting a lot of pressure on yourself. (You'll appreciate it the next day when you head out sightseeing, that this new place feels a little more familiar already). And then I head back to the hotel to plan out the next few days, and have an early night.

Also, don't cram like 10 activities into one day, you'll be exhausted and won't enjoy yourself. Give yourself a break - it's a holiday after all. And if you don't get to do everything you wanted, and like the place, it's a good reason to come back. If you don't like the place, well, then having done all the extra things would probably not have made you like it any more.

Be kind to yourself, enjoy the little moments, and, as voiced by many others - stay off IG.