I've fixed bike chains for people using their own chain tool. Once a couple asked how to start up their camp stove. Pack stuff you can handle, learn about what you need. You need a bike in good working order. Bikes get flats, learn how and what you need to fix a flat.
Bikes have cables which stretch and break.
Learn how to adjust your gears and brakes to take up the slack and learn how to replace broken cables. If you are touring off road, please go through the trouble of learning as much as possible about your bike. I pack a good little First Aid kit. For the number of times I've used mine, you'd wonder why I don't leave it at home and pack a couple bandages. Still I wouldn't do that, though the frequency of use is low, the severity of possible injuries is great enough to always include it.