A long, formal, stately sentence typical of speeches or editorials. The whole 私達の…奪い去る segment is a relative clause pre-modifying 行為, showing Japanese's willingness to stack long descriptive clauses before a noun. 幸せに満ちた ('filled with happiness') uses 満ちる + the た attributive as a reduced relative — 'days (which are) filled with happiness.' ~にとっての turns にとって ('for/from the perspective of') into an attributive modifier via の. ~と言える (potential of 言う) means 'can be called / it can be said.' まさに ('truly, precisely, exactly') intensifies the claim.