5) Donāt invest more than you are willing to suffer in a worse case scenario. This concept of going all in or taking too large a position size will destroy you quickly. People ask me what % to take of a position size. However, as a simple exercise that everyone can understand, I will analyze a situation and say; ok I entered a stock at, say $3.50. I think the absolute worst case scenario it could go down is $0.50 to $3.00 (You should always have a downside risk/loss target as well as upside. This is where I would end the trade if it went against me. Usually i just use a mental stop and do not enter it at broker). If I have 5000 shares and the worst case scenario happened would I be ok with losing $2500 ($0.50 X 5000 shares) ?
Here are some great articles / links on position size. Some have excel or built-in calculators. There is no magic answer, but there are great guides that exist. The question is do you want to research and learn to excel at stock trading or just hope someone tells you an answer?
