For me what convinced me that my HP existed was when I got to step 10. When I was doing step 2 I was at the point where I was willing to believe in the possibility that a power greater than myself could restore me to sanity, but I was not convinced. By the time I got to step 10 and read the promises it was hard to deny.
The beginning of the promises states "And we have ceased fighting anything or anyone—even alcohol. For by this time sanity will have returned." So I asked myself, had my sanity been restored as results of working the steps? Yes, yes it had. At the beginning of my journey step 2 was an exercise in willingness in order to move on to the rest of the steps. It turns out that the results of completing the rest of the steps gave me the proof that convinced me that there was a HP working in my life, and that is when step 2 was actually realized.
Having said that, I admit that my connection to that HP waxes and wanes in my daily life. But that is usually directly proportional to how earnestly I am seeking that connection. Some days I decide I want to run the show again, and that's when I the connection fades or I lose it all together. But I'm also more averse to self-inflicted pain these days and realize that the problem is on my end and so is the solution.
Quote from Alcoholics Anonymous 1st Edition (p. 84)