The market can stay irrational longer than many can remain solvent, but that usually only applies to those using leverage of some sort (either using margin or options).
Common stock holders have nothing to worry about if they have no need or intention to sell anytime in the next few years.
Hold the course as long as you continue to believe in the underlying fundamentals and income growth trajectory. The stock price and PE ratio may drop quite a bit lower, much lower than what many will want to contemplate, and for much longer than what we might think possible, but that will all be irrelevant in the long term if growth plays out as expected. It has happened the exact same way with other companies, and also with Tesla itself already!
Warning: non-tesla anecdote about investing follows (To emphasize a similar situation to Tesla today).
In the early 2010s, Apple Stock was in a curious spot: It’s market cap had increased significantly in the previous decade on the back of giant success with the iPod and the recent launch of iPhone & iPad. However its PE ratio would fall below 10x multiple times (under 8x on an ex-cash basis) between 2011 - 2016, despite the iPhone continuing to grow along with it’s other products & services and the company increasing it’s vertical integration.
All you saw in the finance and tech media was: “Apple is doomed” and “competition is coming“ and “all they are is overpriced hardware, clever marketing & they will run out of fanboys“. Most of the market participants predicted that Apple’s profits would eventually fall and they would never be able to successfully introduce another meaningful product that would “move the needle”.
(Famously, Tripp Chowdry - legendary buffoon - said of Apple in 2014: “they only have 60 days left to either come up with something or they will disappear“)
It was hard to be an Apple investor at that time. By 2016 I thought I was taking crazy pills, the company Enterprise Value was under $400 Billion, while the company was buying back $40 Billion plus in stock a year and still growing its cash pile ever larger (technically at the then market value and buyback rate the company cash amount would surpass its market cap in less than 8 years and its enterprise value would turn negative). I wrote a blog post about it that garnered over 30 thousand views - there were plenty that felt the exact same way, that the outcome was obvious (massive share price appreciation) but why hadn’t the stock market in aggregate not realised the same?
The answer was obvious in retrospect: The stock market is often stupid. When it is, fortunes are made by those with conviction, no matter how long they have to wait.