It's simple really. You use this site at your own risk and I promise not to read your journal, give it to anyone else, or sell your personal information. I build sites like these to solve a problem for myself, and then do the extra work to allow others to solve the same problem. If it helps you, that is great.
Please be aware that I am not a large corporation and I don't have unlimited funds. If the load on the site starts to require additional resources I will look at ways to have the site pay for itself, but this will not include starting to charge you to access your journal entries.
Please also note that I do plan to publish aggregated graphs on the site, such as "today 67% of people say they are happy", but this will never include individual, identifiable information.