Share to me Terraform operation experience

Hello. I have question.
In our project case, we create AWS and GCP resources using Terraform.

I think terraform is very helpful create new or similar resources.
But, today It’s difficult to manage Our resource using terraform.

Cause, our resources are very huge and maybe 1,000 resources are exists.
and if issues happen, using Console is more fast to solve problem.

We know we need to seperate our terraform code.
But we think it’s very difficult and dangerous, cause we have issues a few of resources delete by terraform and can’t sync terraform state file.

Anyway, I want to know tip of terraform operation.
and is it right manage resource using terraform when I operate Service??