Finally things came to a head around age 19-20 when I dropped out of university two years in a row due to depression/anxiety. I had no real problem with school -- but I would just get a month or so in and it would feel unbearable to even think about going to class or opening a book. And I liked school!
After the second time a doctor suggested I start on a small dose of escitalopram. Within a week I was more or less rid of the anxiety, and I think for me an overload of anxiety was what would put me into a depressive state. The biggest thing for me was gaining the ability to have some control over my thoughts. Prior to starting medication my internal monologue was basically just an uncontrollable, irrational, negative stream of consciousness. Since starting, by default I feel... "OK". Which is perfect -- they are not happy pills for me. I still feel negative emotions and I still have bad days but I am able to live my life!
I am still taking 5/10mg alternating daily 10 years later.