I bought my house over 30 years ago, new. More than 15 years ago I replaced the vanity in one bathroom.
While I hadn't done such work before, I had watched my father do all sorts of work on the farm, carpentry, plumbing repairs, concrete, painting, fixing farm implements. The Army in its infinite wisdom considered my test scores and disregarded my college background in American studies to decide that I would best serve the country as a generator repairman. (They then decided I could teach, as they started running both day and night classes, but soon realized my monotone was putting all my night students asleep so shipped me off to a warmer zone.) After buying my house, I decided to save by building some of my furniture, which I did and reasonably well. We still have a couple of chairs.
Finally, although I couldn't refer to the Internet for help, I could go to the Reader's Digest "How To..." series. So I assured my wife and my self that I could do this replacement. Unfortunately I didn't realize how interdependent plumbing systems are. If you decide to replace a 24" deep vanity with a 21" deep vanity (small bathroom), the drain pipe is no longer aligned with the sink drain.
No problem, I went off to the hardware store to find the proper parts. Unfortunately, I failed to measure before I went. And I never asked for help, not on my first visit to the store, not on my second visit to the store, not on the third visit to the store.
The more problems I ran into, the more frustrated I got and the more urgent it was for me to finish the job. So I threw things together, installed everything, spent a couple days trying to remedy a leak at the connection between the sink drain and the trap, and finally called it good enough for government work. And I regret the job every time I look at it.
Fast forward to yesterday, when my long-suffering wife decided she could put up with my replacing the vanity in another bathroom. After we bought the vanity and top, I went to the hardware store and asked for help. I got all the plumbing parts in about 10 minutes. And I'm doing lots of trial runs, dry fitting of the vanity and the plumbing together. I'm also taking breaks, as now, because I still get very frustrated (perhaps more than I used to) when I run into problems (like floors and walls not being perfectly plumb and square).
So I say with Ecclesiastes: Vanity, vanity, all is vanity.