It’s the same reason why people just can’t seem to lose weight, break toxic relationship patterns, or get out of debt. Often, we know what it is we need to do but we just can’t seem to sustain lasting changes in our behaviour. The same goes with the healthy habits of mind (and body) that are proven to combat depression.
Your subconscious programming is determined by everything you’ve learned and experienced. It’s the direct result of the people (and entities) who have influenced you, including your parents, teachers, colleagues, lovers, friends, and even advertisements.
If your subconscious blueprint is not set for success, nothing you learn and nothing you do will make much of a difference on your path to success. Success in this case being a calm, centred, optimally functioning mind, and a regulated nervous system.