"Your schedules are only for guidance.Study your reactions to training from day to day and if you feel jaded or suffer from any soreness allow time for recovery.
Never do speed training when your muscles are sore or you are feeling very tired.Just jog easily,irrespective of what is on the schedule for that day's training.
You can never do yourself any harm by jogging and it will usually help to overcome the soreness or tiredness.
Control your training so that you are not racing it,except when full efforts are called for in the schedules.Run strongly and easily in effort,always keeping something in reserve.As you feel improvement,gradually increase your training tempo but never use that reserve."
Quote by Arthur Lydiard.