why IEnumerator function called twice

Questions & Answers
1

every time I call the IEnumerator function to wait then play an animation it play it two times ,Why?

    void Update()
    {
        StartCoroutine(FightingAnim());
    }

    IEnumerator FightingAnim ()
    {
        bool keyPressed = Input.GetKey(KeyCode.J);

        if (keyPressed)
        {
            timer += Time.deltaTime;
            attacking = true;

            if (timer >= 1.0f)
            {
                m_Anim.SetBool("Holding", true);
                attacking = true;
            }
            if (timer >= 4.0f)
            {
                Debug.Log("Ready!");
            }
        }
        else if (timer >= 0.1f && timer < 4.0f)
        {
            m_Anim.SetTrigger("Attacking");
            m_Anim.SetBool("Holding", false);

            yield return new WaitForSeconds(1);
            // so the player can't move while attacking
            attacking = false;
            timer = 0;
        }
        else if (timer >= 4.0f)
        {
            m_Anim.SetTrigger("Punch!");
            m_Anim.SetBool("Holding", false);
            attacking = false;
            timer = 0;

            Rigidbody2D instantiatedFist = Instantiate(m_Punch, transform.position, transform.rotation) as Rigidbody2D;
            instantiatedFist.velocity = transform.TransformDirection(new Vector3(5, 0, 0));
            Physics2D.IgnoreCollision(instantiatedFist.GetComponent<Collider2D>(), GetComponent<Collider2D>());
            Destroy(GameObject.Find("PunchRocket(Clone)"), 5f);
        }
    }
2

You should set a flag when coroutine is running

private bool isRunning = false;

private void Update(){
    if(Input.GetKeyDown(KeyCode.J){
        TryLaunchCoroutine();
    }
}

private void TryLaunchCoroutine(){
    if(isRunning) Debug.Log("Coroutine can't be launched, already running.");
    else {
        isRunning = true;
        StartCoroutine(FightingAnim());
    }
}

IEnumerator FightingAnim (){

    //.....

    isRunning = false;
}