Pick up the threads
Definition 1 of 2
Pro Tip 1/3Rebuild After Pause
Used when restarting work or responsibilities after stopping for a while. 
She had to pick up the threads of her project after her maternity leave.
Pro Tip 2/3Not Instant
It implies a process to get back on track, not an immediate switch. 
It took him weeks to pick up the threads of his writing routine.
Pro Tip 3/3Continuity
Suggests a link with the past, resuming something previously started. 
The team aimed to pick up the threads where the previous manager left off.