The plan is not the problem
Most losing accounts had a plan. The account was lost in the moments the plan was set aside — after a loss, after a win, when a move was missed, when nothing was happening. Psychology in trading is not about feeling calm. It is about making the decision before the moment, so the moment does not get to make it.
Four failure modes, four rules
Revenge trading
After a loss, the urge to "get it back" produces the next trade too fast and too large. Rule: after two consecutive losses, no new trades for the rest of the session. Write it on the wall.
Fear of missing out
A move you did not catch starts running, and you jump in late with no level and no stop. Rule: if the entry is not on your list of setups, it is not a trade. Missed moves are free; late entries are not.
Overconfidence after a win
Three wins in a row and the next position is twice the size "because I'm reading it well". Rule: position size comes from the formula, never from the last result.
Boredom
Nothing is happening, so you make something happen. Rule: a session with no trades is a successful session if there were no setups. Count it as one.
Your journal is the mirror
The journal column for your state is where these patterns become visible. "Rushed" next to the three worst trades of the month is a finding worth more than any indicator.
Summary
The plan fails at predictable moments. Name them, write one rule for each in advance, and let the journal show you which rule you need most.