The easiest way to leave your emotions outside is to ignore the price of the stock. If you are a long-term investor, it doesn't really matter if the price of the stock moves from $100 to $80 - as long as nothing has happened with the long-term fundamentals of the company.
A common error you can make if you are new is that you may think that a stock with the price of $5 is cheaper compared to the stock with a price of $10. This is however not true since it's the market value that's important.
One way to leave to price of the stock outside is to calculate the annual earnings from a $1000 investment and annual dividends from a $1000 investment. Such as:
|Source: Seeking Alpha|
For example. The current stock price of GE is $20.13. This is the number you should ignore. To calculate the annual earnings from a $1000 investment, you take $1000 and divide it with $20.13 and end up with 49.677. This number tells you how many shares of GE you can buy with the $1000 investment. Now you take the number of shares you can buy and multiply it with earnings per share: 49.677 * $1.225 = $60.85 - to get the final number you need.
Source: Seeking Alpha