OnTriggerEnter2D only one time

How can I execute an OnTriggerEnter2D only one time in the scene?

I’ve made an animated checkpoint that when the player walks beside, it starts an animation, but i would like that this animation could only happen once, any idea what should i do?

bool isFirstTime = true;

void OnTriggerEnter2D(Collider2D other)
{
	if(isFirstTime)
	{
		isFirstTime = false;
		// do something here.
		Debug.Log("Happens only once.");
	}
}