“顺利的”的英语？

那些曾经恋爱不顺利的人都会同情休。Anyone who has been in a troubled relationship will sympathise with Sue.这次平稳顺利的飞行令人难忘。The smoothness of the flight was memorable.即便在顺利的情况下也不要松劲.Don't let down even if the going is good....