I think leading a regular daily life is a very good thing.
Literal
Every-day regular life [object-を] do [nominalizer-の] [topic-は], very good thing [quotative-だと] think.
規則正しい ('regular, well-regulated') is a compound adjective — 規則 ('rule/regularity') + 正しい ('correct'). ~のは…ことだ frames the nominalized action as a topic and evaluates it. と思う marks personal opinion.