A mistake commonly made by people putting together their training programs for fat loss and endurance sports is including too many hard training days in a week. As a basic rule, two principles should be followed for the non-elite: hard and easy days of training should be alternated and endurance training should be 'polarized', that is, easy days spent training around the 70-80% HRmax zone and hard days spent doing interval work above 91% HRmax. If too many hard sessions are performed in one week, excessive fatigue, lowered immune function, loss of motivation and injuries are sure to follow.

Here is a sample training week following the two golden rules for fat loss. Note how sustainable this style of training is. It is still very hard, as goal-specific training should and must be, but it's not only manageable, its may even be enjoyable!

DAY ONE:
Strength Session (HARD)
A1. Deadlifts, 5x12, 30X0, rest 60 seconds
A2. Lying dumbbell press, 5x12, 30X0, rest 60 seconds
A3. Back squat, 5x12, 30X0, rest 60 seconds
A4. Seated row, pronated grip to chest, 5x12, rest 60 seconds
A5. Dumbbell lunges, 5x12, rest 3 minutes

DAY TWO
Aerobic Session (EASY)
7 minute walk
45 minutes at 70-80% HRmax (you can also use your age subtracted from 180 plus 5, should be around 140-155 bpm)
7 minute walk

DAY THREE
Aerobic Interval Session (HARD)
10 minute walk
5 minute progressively increased jog
4x600m at best pace (above 91% HRmax), rest 2 minutes
4x1000m at best pace (above 91% HRmax), rest 90 seconds 
15 minute walk

DAY FOUR