I bought a flight and then had to pay $60 to change it literally two minutes later because I had accidentally booked it at 2am instead of 2pm. I probably mess up at least a quarter of all flights/hotels I book

a travel agent would probably pay for themselves instantly and continuously in your case

when I took the bus from estonia to latvia I had trouble with the ticket scanner but the guy let me on. halfway through the trip I realized I off-by-one booked my hostel and went online to add a day. then I realized I'd also off-by-one booked the bus I was on