Is anything incorrect here?

I'd suggest these changes: >How do you define happiness in your life? >I think **that** happiness is a ~~series of~~ smooth life. What I mean is that there **is** no adversity, hardship **or** suffering. I can get small **amounts of** happiness from ~~a~~ daily life. Also. It is **worth** ~~of~~ doing lots of challenges every day. **That way,** we can **have** more interesting experiences in the future.

"I think happiness is a series of smooth life." - you do not need the "the" before happiness here. Also the end "...is a series of smooth life." does not make sense. A series is multiple things. A smooth life is a singular thing. So you need to either remove series and say something like "...is a smooth life" or change the ending to be plural "....is a series of smooth moments in life." Something like that. "What I mean is that there \[is\] no adversity, hardship\[,\] \[or\] suffering." Each item in this list is singular so the verb must match. Some places don't teach the oxford comma but it is more clear that the last two items in a list are separate things if you have a comma there. And because you're talking about each item individually you need or not and. "Also." - A sentence must have a subject, and a predicate. So you would connect this to the next sentence. "We can \[have\] more interesting experiences in the future." -