Volunteer position

So ladies I am posting this more so to vent not so much fix or change things. Here it goes...

Back in February I started a volunteer position with the local police department. I have to sign up for 4 shifts a month. I completed the training academy and had been on a total of 9 calls in the months I was there. The shifts I had just hardly ever got any calls. I tried signing up for more but even then the callout were few in between. Today they finally let me go stating that I just didn't have the proper experience at this point for to be a team leader for the new volunteers and didn't have the availability.

I want to note they were polite, respectful, and very professional about this. I asked if I was in good standing and they said yes and could return in the future when I simply have more time to volunteer and lived a little closer. I am no upset and totally understand why they let me go.

Now the part that I'm struggling with is feeling guilty (I signed up with the intention of being there for a few years) and feeling like a total failure. I'm fairly young and I've never had too much confidence in the work place. I feel like everything I try I fail no matter much effort I put in. When I fail it feels like a inconvenience to others and like they think I don't care.

Even tho I was not fired or terminated and was dismissed on friendly circumstances I can't help feeling like its 100% my fault. How can I move past this feeling? How can I improve myself so I feel adequate when it comes to the next position whether it be volunteer or work related? I am tired of feeling like I can't find my niche or talent. I know I must be good at something but obviously not have found it yet?