FastLED breathing effect with max brightness

I have a problem. I am controlling my WS2812B using an Arduino, but I have a problem with the breathing effect. I created a class in the code that looks like this:

String breathDirection = "Down";

void breath_effect()
{
fill_solid(leds, TOTAL_LEDS, primary);
float currentBrightness = FastLED.getBrightness();

if (currentBrightness <= 1)
{
  breathDirection = "Up";
}
else if (currentBrightness >= brightness)
{
  breathDirection = "Down";
}

float brightnessCorrection = static_cast<float>(brightness) / 200;
if (breathDirection == "Down")
{
  currentBrightness = currentBrightness - brightnessCorrection;
  FastLED.setBrightness(currentBrightness);
}
else if (breathDirection == "Up")
{
  Serial.println("Binnen");
  Serial.println(currentBrightness);
  currentBrightness = currentBrightness + brightnessCorrection;
  Serial.println(currentBrightness);
  FastLED.setBrightness(currentBrightness);
}
}

Now the breathing effect only works when the brightness variable is set to 200. If I set it on a different value below 200, it goes down, but never comes up. The currentBrightness is each round the same value. What is going wrong here?

You need to set global variables:

//Global scope:

const float _brightInterval = 1.0f;
const float _maxBright = 255.0f; //i'm not sure whats your max bright here
const float _minBright = 1.0f;

float _brightness = _maxBright;

And instead of strings i would use states. It's faster and saves memory.

enum states
    {
        hold,
        down,
        up
    };
states _state;

then in the loop do something like this:

switch (_state)
    {
    case states::down:
        _brightness -= _brightInterval;
        break;
    case states::up:
        _brightness += _brightInterval;
        break;
    case states::hold:
        _brightness -= _brightInterval / 10.0f; //hold makes it go down but in a lower rate.
    default:
        break;
    }

    if (_brightness >= _maxBright)
        _state = states::hold;
    else if (_brightness <= (_maxBright - 50.0f) && _state == states::hold)
        _state = states::down;
    else if (_brightness <= _minBright)
        _state = states::up;

FastLED.setBrightness(_brightness);

Try to change those values to achieve your desired effect. The (_maxBright - 50.0f) in the second if, is the step when it starts to accelerate down. change it to maybe (_maxBright - 10.0f)