The faster you get rid of this belief that you can just push throu it and hence accept the reality of it, the better as that false belief often leads to the worsening of this condition and that is something you certainly do not want happening. Any exercise which has you in a lower health state the next day... certainly was over done. Work out how much you can do.. without there being negative impacts as lowering your health state thou your exercising, isnt healthy. Exercise in a healthy person increases oxygen, blood flow etc but often is doing the opposite in a CFS/ME person. Instead of feeding cells, they are being starved.