A while back, a fellow writer confessed that she tried to keep a journal but found that she had a tendancy to sugar coat everything she wrote. When I asked her why, she said, "I just can't force myself to write down my deep, dark secrets? I try to tell myself that the journal is for my eyes only, but what if I die tonight and my children find it?"
Although I find it helpful to look back on journal entries a week, a month, or a decade later; the most beneficial aspect of keeping a journal is to get the thoughts out of my head and onto paper. It's not mandatory that your journal become a permanent record of your life. The process is enough. So if you're in the category of those who are shy about revealing all, write it down and then shred it. Another answer is to use your journal for writing practice sessions rather than for revealing the secrets in your heart.
Tip of the Day: If the potential content of your journal is too hot to handle, write it down to enjoy and benefit from the process of jounaling and then shred it.