A company's stock price has nothing to do with its value. A $50 stock can be more valuable than an $800 stock because the share price means nothing on its own. The relationship of price-to-earnings and net assets is what determines if a stock is overvalued or undervalued. Companies can keep prices artificially high by never conducting a stock split, yet not have the underlying foundational support. Make no assumptions based on price alone.
What would make me sell: Sometimes there are good reasons to split up. For this part of your journal, compose an investing prenup that spells out what would drive you to sell the stock. We’re not talking about stock price movement, especially not short term, but fundamental changes to the business that affect its ability to grow over the long term. Some examples: The company loses a major customer, the CEO’s successor starts taking the business in a different direction, a major viable competitor emerges, or your investing thesis doesn’t pan out after a reasonable period of time.