The making of an essay

When a essay was due throughout the week I’ve had very good experiences and bad ones. I’ve been able to write things down and brainstorm as I go, but recently things haven’t been like that. I’ve had teachers give me topics on what to write on. I do as I’m told but if it does not make sense to me I struggle bad. I write nonsense and it doesn’t match. I’ve had bad times but when it is good I tend to overwrite it.