I was 'secure in the belief/knowledge' that I had done all I could. [=I felt confident because I believed/knew that I had done all I could]
They are 'financially secure'. [=they have enough money to live on; they do not have to worry about money]
You can access your bank account online using a 'secure' [='secret'] password.
(..) You can literally talk to my subconscious. That's one of the ways we extract information from the subject. How else do you do it? By creating something secure, like a bank vault or a jail. The mind automatically fills it with information it's trying to protect. - You understand? (..)2010 Inception