To give you a idea of the 'variance' you can expect as a 2bb/100 winner over 25k hands
Click to see full-size image. |

Each line represents what your graph would look like in terms of profit/loss.
Note the black dotted line is what a true 2bb/100 winrate would actually look like.
So what you can take away from this is that over such a small sample, its extremely easy for you to think your much better/worse than you actually are.
This is why you need large samples for your true winrate to actually converge.
Using half a million hands we get this graph
Click to see full-size image. |

Ok, they are not sticking entirely to the true winrate, but the general trend for each of them is upwards. Unlike our previous image. Where you could have the illusion of being a huge crusher/fish over such a short sample