Hey I would try to access the horizontal movement only when the player is doing a jump. Something like

    if (CrossPlatformInputManager.GetButtonDown("Jump") && hasJumps > 0)
    {
        double jumpHorizontalVelocity;
        if (CrossPlatformInputManager.GetButtonDown("MoveRight")) {
            jumpHorizontalVelocity = jumpHorizontalSpeed;
        } else if (CrossPlatformInputManager.GetButtonDown("MoveLeft")) {
            jumpHorizontalVelocity = -jumpHorizontalSpeed;
        }

        Vector2 jumpVelocityToAdd = new Vector2(0f, jumpSpeed);
        myRigidBody.velocity += jumpVelocityToAdd;
        myRigidBody.velocity.x = jumpHorizontalVelocity;
        isJumping = true;
        --hasJumps;
    }

    if (!myFeet.IsTouchingLayers(LayerMask.GetMask("Ground"))) { return; }
    {
        hasJumps = 1;
        isJumping = false;
    }