Looking back, I guess I had the same fear as you in the beginning. But once I understood how houses were built, that fear completely went away.
Its a lot less intimidating once you understand that a house just consists of:
1. A foundation
2. Some walls
3. Roof
4. Heating / cooling system
5. Hot and cold water lines that run from the water source throughout the home to everything that needs water
6. Wiring that runs from the power source (panel) throughout the home to everything that needs power
7. Insulation in the walls
8. A bunch of finishes to make it look pretty (drywall, paint, floor tile, cabinets, countertops, light fixtures, backsplash, sinks, faucets, bathtubs, etc)
Not much else to it. And if anything ever goes wrong, most things are easy and inexpensive to fix. I recommend you watch some YouTube videos that show houses being built so you understand what is going on behind the walls. And as @Nathan A. suggested it would be good if you could get some hands on experience as well. But don't let this fear hold you back. There is always a handyman or contractor out there to fix any issue that could ever be needed on your home.