Where did you mess up? It would be great if you can open a scam accusation or give more information about the service since it will help members from repeating the same mistakes.
I looked at his first post (only has two posts at the time of writing), and it seems that he used a fake mixer called coinmixer dot es. It's sad that these things happen, but hey, the best way to learn is to lose money and from there improve. I hope it wasn't a lot, but still, it sucks regardless of the amount.
I always stick to one mixer, which used to be Bitmixer back in the days, and now
ChipMixer. I might look like a shill considering my signature, but you'll like the experience there with the various chip sizes you can withdraw at any given time. Try with a small amount first, and see for yourself how it works.