If you've invested into many coins, it may be quite helpful to get yourself a free Google spreadsheet over at Google Docs to automatically track the progress of each coin. Simply paste the following formula into the document, which I got from stackoverflow.com:
=IMPORTXML("http://coinmarketcap.com/currencies/bitcoin/":"//span[@id='quote_price']")
Please do your due diligence about this formula. I am a new forum member and you should not trust me. What this formula does is that it imports the data that is displayed on a website. In this case, it imports of the current price of a specific coin.
It will help you to keep track of the price developments of each coin.
What I do next is that I set myself a warning that notifies me, as soon as a certain coin drops to a specific price. Let's say for instance I've bought bitcoin at $10,000. In this case, I set myself a warning for $11,500, which gives me enough time to sell at a profit in case there are negative developments.
As soon as a specific point is giving me red lights, I begin investing why this is the case and will plan my decisions accordingly.