DIY HVAC cleaning breaks system

I was reading online how your HVAC system should be cleaned out and serviced once or twice a year.

I am kind of handy with a tool belt so I decided I should just do it myself.

I watched lots of videos and read up on everything. Then I got to work with my tools, a vacuum and some oil. I took my time and was very careful but when I put everything back together, my HVAC system simply would not turn on. I took it apart again and looked at all of the connection but everything was right. I knew I had to call in the professionals. This was over my head. A real HVAC company came out the very next day and the technician took one look at my HVAC system, flipped a switch on the side, and said, “well here is your problem.” I felt so stupid. I had simply turned off my HVAC system like you might turn off a light switch. The switch must have gotten bumped when I was moving things around. It might have even gotten caught on the cleaning rag or something. I did not even know there was an off switch. Other than that, the technician said I did a good job cleaning, for the most part. He gave me some hints and tips for next time but he also indicated that his company cleans HVAC systems for very little money. It sounded like a good deal but I kind of just want to do it myself. How else will I ever learn?

Commercial air conditioning system