I recommend you see this discussion on manifestation:
In short, simply by telling ourselves we can achieve something doesn’t mean we will get it. We still have to work for it. Secondly, there are some people who work hard for it but they still don’t get it, so we still need Allah’s blessings. Third, we want Allah to bless what we do. If He doesn’t, we may get what we desire but we may end up serving Iblis instead of Allah.
To know that we are on the right path, you may see this video:
Others might do some unusual spiritual acts, but it doesn’t mean they’re on the right. The world of souls has certain laws and ways of working and to an extent even non-believers can access some of it. Yes it’s possible for one to feel spiritually low.