A handful of times. Identifying the root cause helped a lot, along with a period on SSRIs to bring negative thoughts down to a manageable level. In hindsight, worrying too much about the opinions of others was essentially the root cause, though it wasn't at all obvious to me at the time. Without getting too detailed, this led to a period of lying, alcoholism, partying to maintain shallow relationships, job hopping, and general escapism. It became a self-sustained spiral that continued to make things worse.
What eventually helped was setting smaller goals, which turned into bigger goals, and eventually into a sense of purpose. These days it’s more like weekly or monthly ups and downs, which feels normal. My personal rule when things dip is simple: movement. Do something. Knock one thing off the list.