I tried keto (to the extend it was possible without sacrificing every social event) and found that it ruined my cognitive ability. This is known as the "keto flu" and it made me sluggish, tired and gave me headaches. I just wasn't able to function properly. Naturally I am not condoning high carbohydrates diets, but I a variated diet with slight deviations based on personal preferences (and seasonality). I do tend to avoid to many carbohydrates and eat more green, fruit, meat and dairy products.