不行，今天不知為何沒有幹勁。

It's useless, I'm not motivated today for some reason.

Source: Tatoeba

Sentence Composition

1 不行 bùxíng
  1. won't do
  2. be out of the question
  3. be no good
  4. not work
  5. not be capable
2 今天 jīntiān
  1. today
  2. the present time; now
3 不知 bùzhī
  1. not to know
  2. unaware
  3. unknowingly
  4. fig. not to admit (defeat, hardships, tiredness etc)
4 為何 wèihé why
5 沒有 méiyǒu
  1. haven't
  2. hasn't
  3. doesn't exist
  4. to not have
  5. to not be
6 幹勁 gànjìn enthusiasm for doing sth