Broken Workflow "if this Workflow has any Running instances, changing this custom task may break those workflows"

I made this great Designer Workflow and customized the workflow aspx page with my XSLT and other custom modifications. All was great untill I decided to Change one of the workflow fields.
FYI - I was using "Collect data form User (Output to Variable)" action and the fields were created in that data collect form. When I decided to change the fields I got this below error or lets just say popup.
 "If this Workflow has any Running instances, changing this custom task may break those workflows"
I said ok what harm It can do but I was wrong. I clicked this popup and it switched my customized form to its orignal form. Yes it was Workflow form that I customized highly and I lost all the changes.

So beware while clicking "If this Workflow has any Running instances, changing this custom task may break those workflows" because it may remove all modifications from your workflow custom farms.