Believe me when I tell you, you won't lose conditioning when you taper. On race day, however, you're going to need to control any impulses to run the first few miles too fast. Maintain the same pace as your usual weekend runs. One of the reasons for these long runs is to get your body used to moving for a long period of time, as well as distance. If you cut the time length of your workouts short by running too fast, you spoil the effect of the taper and don't get full benefit.
Marathon running is a psychological, as well as physical, game.
Keep the bike ride gentle. Swim more to loosen your muscles, not strengthen them. And if you've been doing strength training, you might want to stop, or do very little, with the marathon almost in sight. Walking remains a good off-day exercise for runners. That's because in building to a mileage peak, they often overdo it and temporarily suppress their immune systems.