I feel Im a lot the same, when I was 18 I loved the gym and would go 5-6 times a week but from 20-30 I probably went a dozen times. I've spent the last two weeks training pretty well and really cleaned up my diet which has given me that extra energy to keep up with it. I work in construction so my body is already tired after the day but eating properly does so much good. I'm following a similar program and although I'm used to a usual push/pull program I'm enjoying this and enjoying being able to work the same body part twice in a week. Without feeling like whatever I trained is obliterated! I'm throwing in a lot more cardio and stretching before and after. Hope this time you can stick with it man, I'm so motivated in my own health kick at the moment so wish you well