I always keep track of the price of two coin ETH and BTC, and when they fall to the most reasonable price I buy and hold waiting for reasonable price to sell
You should also watch the till-date charts of bitcoin and ethereum. They reveal a lot about the ups and downs and when it is going down and when its going up. Use them to identify the point where you should buy/sell/hodl.
I have good planning ahead, I am going to buy some coins and will earn good profit ahead because this is the downtrend and some peoples point this is the full downtrend and next coming days it will go up and provide the good amount in return that is why i have planning to invest and earn profit ahead,
There is guarantee that the coins you are going to buy are going to be in uptrend in future. I hope you are doing proper research and analysis before investing money into them. For example most altcoins will bleed out and there is a typical despair going on in every social media about all the ICO tokens. But then top few altcoins and bitcoin will stand their ground.