swordfish2011

I say you split it into weekly baby steps, something like this:

Week 1

1. Start with an easy flat ride of 10-15 km.
2. Relax for a day
3. Another easy ride of 15-30km with some small elevation gain(~50-100m)
4. Relax
5. A longer ride of 30-50km with a higher elevation gain (~100-250m)
6. Relax
7. Relax

Week 2

1. A flat ride of 15-20 km.
2. Relax for a day
3. Another ride of 20-50km with some elevation gain(~100-200m)
4. Relax
5. A longer ride of 50-100km with a higher elevation gain (~200-350m)
6. Relax
7. Relax

and keep increasing the numbers as the weeks pass by.
I really hope you get your motivation back and wish you all the best, and good luck!