Reduced effect of breathing over time

So as the title says, when I first started the breathing several months ago It would really clear my mind and I would feel great , but as time as gone by I have noticed the effect wearing off. The physical benefit of the breathing is still good I can run and exercise better than before, but the mental benefit and increased energy I was getting seems to have gone back to base line. I suspect that I am not hyperventilating as much as I was since I don't experience the tingling fingers and toes like I used to. I have tried different breathing techniques (nose breathing, slower faster, more rounds etc) but nothing really seems to be effective. I feel like a drug user wanting to get back to the highs of those early days! Anyone have any thoughts?