Choosing repertoire is hard, but a good teacher can help you pick out pieces that are suitable for you. If you’re sans teacher, you’ll have to choose your own repertoire.
Guitarists seem to have the idea that it’s better to play entire programs of very hard stuff all the time. That’s okay, if you’re Jorge Caballero or John Williams or Craig Ogden or (insert your great player of choice). The rest of us can benefit from this simple tip:
Your repertoire should include a variety of difficulty levels. Some very easy pieces, some hard stuff, and some things right in the middle.
There’s something great about playing simple music that’s hard to ignore. The easy stuff can be used to show off your musicality; the hard stuff will push your technique along. When in doubt, favor putting more easy pieces into your repertoire.