I do look more at the buying price ,then worry about the selling price. I have moved away from trying to time the market, to just look at spending a long time in the market. Buy with the intention to hold for quite some time. If the price goes down that gives you more shares in a quality company at a discount. If you are buying with the intention of selling short term, then have a clear idea of your take profit/stop losses.
It is incredibly hard to time the market. You will have success for a while, but sometimes markets can behave in a very irrational way. And the can stay that way longer than you can be solvent. Avoid leveraging in general, and buy to hold.