Something always comes up when things seem to be going well in life.
For some reason, there is always something that derails us when things are going smoothly.
ご質問ありがとうございます。
① "Something always comes up"＝「何かがいつも起きる」
"when things seem to be going well in life."＝「人生で物事が上手く行っていると見えるときに。」
② "For some reason,"＝「なぜか」
"there is always something that derails us"＝「何かが私たちの行動を脱線させる」
"when things are going smoothly."＝「物事が上手く行っているときに。」
ご参考までに。
Whenever things are going well at work or in romantic relationships, something always comes along to slow things down, and I don't know why.
この場合、次のような言い方ができます。
ーWhenever things are going well at work or in romantic relationships, something always comes along to slow things down, and I don't know why.
「仕事や恋愛でうまくいっているときはいつもなぜか毎回邪魔が入る」
to go well at work で「仕事でうまくいく」
to go well in romantic relationship で「恋愛でうまくいく」
something always comes along to slow things down は直訳すると「何かがいつもやってきて物事を遅らせる」＝「いつも何かしらの障害がある・邪魔が入る」と表現できます。
ご参考まで！
アメリカ合衆国 
カナダ 
