There's nothing necessary to quit bitcoin trading, because if you can spend more time over the observation of price movement even if price goes down, can make a profit out of it.
but there are some people who spend most of their time observing the pricing and still they are unable to predict that what will be the future of that coin and how much will it increase in value in the coming future.
Yes it is true that observing the price movement you cannot find what will happen next, you have to keep eye on the coin development , where it is updating it progress on the project, as if you are fully aware of the coin details then only you can make decision of holding or selling it.
Trading is something you have to do some research on coins details and its development and project which it is going to launch and if their you find any negative response even if you are in small loss you should sell it because getting full loss is better to take small loss.