keystone

a central cohesive source of support and stability; "faith is his anchor"; "the keystone of campaign reform was the ban on soft money"; "he is the linchpin of this firm"

आयुर्वेद के अनुसार मानव शरीर चार मूल तत्वों से निर्मित है-दोष, धातु, मल और अग्नि।

Doing things honestly has been a keystone of his life.