I was the same when I started the couch25k app but I also suffer from seizures and have to run alone
My local park run will not allow me to partake as I may damage another runner, they think it's best that I run on my own so even if I get a warning sign and want to stop being on my own means that I have to carry on till I'm near my home to then ring for help
Run what you feel is best and If you feel too tired then pause the app and take a break but you will then want to stop anyway, most of the tiredness I found was in the mind so found other things to think about to try to spur me on, try giving yourself a goal of sat week w3d3 and then when you complete the run give yourself a reward ? May keep your enthusiasm up
Good luck