Many people fail when they attempt withdrawing from antidepressants because they get too woozy or depressed. The pharmaceutical companies just tell you to withdraw gradually. They give you no guidance on increasing serotonin levels naturally because this knowledge wouldn't help their profits. Many patients become massively depressed and even crazy during the withdrawal period due to extremely low serotonin levels in the brain.
After quitting cold turkey, my advice would be (1) to take fish oil for a month before withdrawing and (2) take one or two tablets of 200 mg of time-released 5HTP daily. Natrol is a good brand.
Also, figure out the core cause of your depression. Dr. Blaylock has a great video on this topic. Depression is generally caused by inflammation in the brain. Enzymes stop producing serotonin in the presence of inflammation. Brain inflammation can either be caused by an omega 3 deficiency, a chronic illness, heavy metal toxicity (like lead or mercury), or chronic pain.
Many people suffer from an omega 3 deficiency these days because seafood is prohibitively expensive, and because most farm animals consume corn. Corn-eating cows or chickens produce ten times less omega 3 fats than grass-eating cows or insect-eating-chickens. Corn, peanut, and soybean oils give you inflammatory omega 6 fats instead of anti-inflammatory omega 3 fats. The solution is to take a fish oil supplement daily and replace seed oils with coconut oil, olive oil, and grass fed cow butter in food. Also, vegetables are anti-inflammatory while red meat, refined carbohydrates, and sugars are inflammatory. Thus, change your diet accordingly.