plain sailing

noun

1. Navigation. sailing on waters that are free of hazards or obstructions.Compare plane sailing.
2. an easy and unobstructed way, course, or plan: As an heir to a large fortune, he looked forward to financial plain sailing.

noun

1. informal smooth or easy progress
2. nautical sailing in a body of water that is unobstructed; clear sailingCompare plane sailing

Easy going; straightforward, unobstructed progress. For example, The first few months were difficult, but I think it’s plain sailing from here on. Alluding to navigating waters free of hazards, such as rocks or other obstructions, this term was transferred to other activities in the early 1800s.