How to cancel a workflow token from within a workflow?

Hello,

I have a called "Workflow failure monitor" in which it every 5 minutes it gets a list of Sorted Executions for a given workflow. If there's a token in a failed state it sends an email & txt.  This morning I noticed there were roughly 800 tokens in a running state for the workflow "Workflow failure monitor".  The workflow only takes 1 second to complete and I have no idea why the initial and subsequent tokens stayed in a running state.  My thought was:

1.Get the Sorted Executions for the workflow "Workflow failure monitor"

2.Loop them looking for !=complete, !=canceled and !=failed as well as excluding the current workflow run

3.If a token was found matching the criteria from #2 above, I would cancel it.

However, when testing the cancel() method of a token I get an error of "Cannot cancel workflow".  The code for the cancel routine is below.  Thank you for your help!

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  var wfs = new Array();

  wfs.push(workflow.rootWorkflow);

  var tokens = System.getModule("com.vmware.web.webview").getSortedExecutionsForWorkflowList(wfs,null);

  System.log(workflow.id);

  // Cancel any running workflow tokens of this workflow

  for(var i=0; i < tokens.length; i++)

  {

       if (tokens[i].state != "completed" && tokens[i].state != "canceled" && tokens[i].state != "failed")

       {

            if (tokens[i].id != workflow.id)

                 tokens[i].cancel();

       }

  }