You and I have a similar dilemma. The overall universe of ppl seeking self-improvement is huge. For example, http://www.selfgrowth.com/ shows that they have 2 million visitors per month. The challenge for you is that the group you’re seeking is a sub-niche of the overall niche.
For me, the overall universe of ppl who want to lose weight is also incredibly large. But the ppl I’m most interested in (the 15 million ppl that the NIH says are 100 pounds or more overweight) are a sub-niche of that group. Will my information work for anyone wanting to lose weight? Of course. But targeting the sub-niche is my goal.