To do something completely (unintentionally); cannot help doing

used in response to a failure or mistake: dang, shoot, darn it

sister city

be cut off, break, snap, burst, collapse / be cut, be injured, become fissured / break off, be interrupted / cut or sever connection with / run out, expire, terminate

be able to do, be able to finish

Same as above.

cannot completely... (because it's excessive)

start

a start

start! begin!