Making plans is needed to have successfull trade. Without plan, you're giving away your holding out of you.
Planning is a must, it should be a stupid idea to trade without planning. Actually, it is not only about making a plan, but we must also learn everything related to trading firstly. I cannot imagine that someone tries to trade without having the proper knowledge. Trading without a plan & proper knowledge seems like fishing without a hook.
"Invest what you can afford to lose"
I invested what I actually I didn't regret, it is the way how you want to learn about mistake to us to become more careful the next time you it next time.