FPS Camera, Camera and Player conflicting...

I didn't want to use the inbuilt script or copy a script from another Answers thread so please don't post a different script, I'd like to figure out the issue so I'm able to learn from it. I've created this script that I placed on my Player (Parent) and Camera (Child), I enable the Y on the Camera and the X on the Player but it seems to be cancelling the Player out.

 using UnityEngine;
 using System.Collections;
 
 public class PlayerAiming : MonoBehaviour {
 
     [Header("Toggle")]
     public bool isX;
     public bool isY;
 
     [Header("Sensitivity")]
     public float Sensitivity;
 
     private float yRotation;
     private float xRotation;
     private float curYRotation;
     private float curXRotation;
     private float yRotationV;
     private float xRotationV;
     private float Damp=0.1f;
 
     void Update () {
         yRotation += Input.GetAxis ("Mouse X") * Sensitivity;
         xRotation -= Input.GetAxis("Mouse Y") * Sensitivity;
         xRotation = Mathf.Clamp (xRotation, -90, 90);
         curXRotation = Mathf.SmoothDamp (curXRotation, xRotation, ref xRotationV, Damp);
         curYRotation = Mathf.SmoothDamp (curYRotation, yRotation, ref yRotationV, Damp);
 
         if (isX) {
             transform.rotation = Quaternion.Euler (0, yRotation, 0);
         }
 
         if (isY) {
             transform.rotation = Quaternion.Euler (xRotation, 0, 0);
         }
     }
 }