Originally posted by: briti_asfiya
la hoal wala kuwat is a part of the longer sentence la hoal wala kuwat illa billah that roughly translates into, "there is no power and no strength except with Allah." It essentially talks about the progress that can be achieved with transformation and no transformation can occur without the will of Allah.
Astagfirullah is a short prayer of redemption, seeking Allah's forgiveness.
My friends, and I guess everyone, use it as an expression of disapproval if we say something that we should not, that's what my friends do.