Subject + 本来 + Original Plan, 可是/但是 + Actual Outcome
本来 (běnlái) as an adverb means "originally" or "was supposed to," indicating that a situation has changed from its original state or that something did not go as expected. It often implies a contrast between what was planned and what actually happened. It frequently pairs with 可是 or 但是 to introduce the changed outcome.
我本来想去看电影,可是突然下雨了。
wǒ běnlái xiǎng qù kàn diànyǐng, kěshì tūrán xià yǔ le.
I was originally planning to go see a movie, but it suddenly started raining.
她本来要来参加聚会的,但是临时有事。
tā běnlái yào lái cānjiā jùhuì de, dànshì línshí yǒu shì.
She was originally going to come to the party, but something came up at the last minute.
这个周末本来打算休息,结果加了两天班。
zhège zhōumò běnlái dǎsuàn xiūxī, jiéguǒ jiā le liǎng tiān bān.
I was originally planning to rest this weekend, but ended up working overtime for two days.