We may think that our thoughts are only for , but unconsciously they other lives, richly or adversely.
The sentence contrasts what we assume about our thoughts with what they actually do to others. "Only for ourselves" sets up the contrast with "other lives," and "influence" matches "richly or adversely." So "ourselves ... influence" is the fit.
ourselves ... influence is the answer.
If the price of a commodity increases by 25%, by what percentage should the consumption be reduced to keep the expenditure the same?