I think, firstly the right knowledge and understanding of a particular trade should be noted and continuous practice (demo) and to know how a particular trading works and it's pattern , all this comes with continuous practice (demo) even before using your money to start a trade...understanding and right knowledge really matters....
Understanding and knowledge are like a direction for every trader so as not to walk on the wrong path in trading because the wrong path can result in losses to the point of losing money that has been used as initial capital. I also consider these two things more before starting trading and also other things because in every job there must always be a deeper level of knowledge and understanding so that the results can be better and not seem like throwing money at the job. So these two things are clearly very important and should not be ignored by any trader.