Mental Freshness - keeping a positive mind during marathon taper

During the taper period of a marathon training programme in the past, it hasn't been the physical aspect that has affected me (the hard physical toil is mainly complete) - it was the mental pressure and affect of sixteen weeks or so high mileage and intensity training now winding down and having to "hold your horses" for the big day!
Usually during this period,one of two things usually occurred (none of which were beneficial to my marathon!). I either took the foot of the gas completely, training and diet wise convincing myself that the hard work was already done and then surprised as to why three weeks of this behaviour resulted in a sluggish, struggle-filled marathon or I kept the intensity high and faced the inevitable burn out on the day resulting in massive frustration come the end of the marathon.
This time out however, I remain focussed on that marathon day itself and have remained mentally positive whilst doing all the other things such as nutrition and training correctly. Most miles are now at marathon pace to get myself so accustomed to this pace that it is nearly in my subconscious come the big day.
Sleep and nutrition have also taken on an even bigger priority also as those extra calories are not being burned off as much due to downgrading of long miles and there is little point in packing on the lbs three weeks out from a marathon,jeopardising the result.
Hopefully, all this will reap dividends when I face that final turn down the home straight on marathon day!