I agree that some self-diagnosis is okay, however, there are times when we have to go beyond self and seek professional intervention, or we may end up fighting a battle with the wrong set of weapons (and wasting precious money). I'll give 2 personal examples:

1. Some years ago I diagnosed myself as having a cold and self-treated. Now, I knew I also suffered with allergies, but wasn't alarmed at the symptoms until something in the back of my mind insisted I see my GP. Turned out I had a really bad respiratory infection.
2. As a child, I knew I had depression. I dealt with it on my own. In my late 30s I started experiencing symptoms that suggested I had low blood pressure then low blood sugar then low iron. None of these were strange to me. So I adjusted my diet and kept adjusting until I thought I saw improvements. But those "improvements" were always fleeting. I was unemployed and very low on money, so going to the doctor was out of the question, until I realized I could no longer "read" my environment and felt I had lost touch with my surroundings. I listed all my symptoms, including the physical ones and went to my GP the next day. That's when I received the official diagnosis of major depression and enlightenment on the physical effects of an illness I always thought was purely mood related.

Going to the doctor can be really tough when you have no money. But, where possible, seeking medical help is important especially when you feel your health spiraling out of control or you haven't felt like your usual self for a while.