Workflow approval Status cannot be changed

Hello there

I have created a ledger daily journal workflow

it has a simple condition for approval

if my amount is above 1000 USD it will follow a approval path ...or else it will end

the workflow works fine when following the approval path

but I get the error " workflow approval status cannot be changed".

when the amount the less than 1000 and I am not able to post the journal since the post button is greyed out

Thank You

Kaushik