AWS Simple workflow notification technique

I'm new to AWS SWF and my task is to give notification(thru email) when an activity fails during first attempt ONLY. I'm using Settable<Boolean> as my flag but the value is not reliable because the workflow is running async. Here's my code:

 final AsyncExecutor asyncExecutor = new AsyncRetryingExecutor(retryPolicy, workflowClock);
 final Settable<Boolean> notifyException = new Settable<>();

    new TryCatch() {
        @Override
        protected void doTry() throws Throwable {
            asyncExecutor.execute(() -> new TryCatch() {
                @Override
                protected void doTry() throws Throwable {
                    Promise<ActivityOne> activityOne = activityOneClient.performAction(activityOneRequest);
                }

                @Override
                protected void doCatch(Throwable e) throws Throwable {
                    if (!notifyException.isReady()) {
                        // PERFORM notification service here!!
                        notifyException.set(true);
                    } else {
                        // DO NOTHING. Notification is already sent the first time :)
                    }

                    throw e;
                }
            });
        }

        @Override
        protected void doCatch(Throwable e) throws Throwable {
            System.out.println("======");
            System.out.println("CATCH ALL!! " + e.getMessage());
            System.out.println("======");
        }
    };

The notifyException 's value is always changing even though I explicitly set its value to true inside if statement. The result of my code is it will perform more than 1 the notification service.