Is this something new to you? If so, your body/metabolism is going to go through an adjustment period before getting used to a keto style diet. The lethargy gets more bearable after awhile and the carb days will actually give you a huge boost. My most hazy, zombie-like times are the days right before carb days when I'm the most carb depleted. I feel way more fatigue in the gym and have a bit of a mental block, then a great two day boost after refueling.