John Jr. Can't do math either
New Math gave rise to a convenient new dichotomy: there are those people who can do math and those who cannot. Little Johnny concluded that he must not be good at math, so he placed himself in this second group. His math studies came to a screeching halt and he spent the rest of his life avoiding math at all cost.
Twenty years later, John Junior begins his own math studies. Like in any other endeavor, if Junior had had high expectations and ample encouragement in his study of mathematics he would have likely gone far. The second he hears John Senior state that he was never good at math, however, Junior immediately lowers his own expectations. With lower expectations comes less effort, which in turn brings less success. His low expectations turn out to be self-fulfilling prophecy, and in a few short years we hear John Junior bragging to his friends that he also is "not good at math."
The problem with this dichotomy is that it is completely false. Yes, some people appear to have greater aptitude for abstract thought than others. Some people learn math faster and seemingly with less effort. It might even be that some people are just "better at math" than others. This in no way implies that the less "gifted" cannot excel at math. Almost anyone can, given enough time and effort.
This is not to say that math will come easily to everyone. It might not. In fact, every student out there will eventually reach a point in their studies where math gets really hard. At this point further progress takes considerable work and sacrifice. It is still possible, however, if the student is properly motivated and believes that they will be rewarded for their persistence. No such progress will ever be made if the student quits trying for lack of confidence. The self-label "not good at math" might make a student feel better about having to struggle with their math studies, but is cripples their belief that they will succeed if they work hard enough.
I should take a moment to acknowledge that there exists a small percentage of students out there who are not wired to succeed at abstract math. Legitimate learning disabilities do exist and can prevent a student from excelling in their math studies, especially with the more abstract material that we begin to see as we move farther into the high school curriculum. For the vast majority of people who self-identify as not good at math, however, the limitation stems not from a lack of latent ability, but rather from their low expectations and lack of confidence in their ability to achieve success through hard work.
As teachers or parents of young students, it is crucial that we remain conscious of our own academic biases. If we want our children to succeed in their studies, we need to not only set high expectations and provide ample encouragement, but we must also control the destructive influence of our own insecurities and negative attitudes. You don't have to lie and claim to love a subject that you actually loathe. Just re-frame your opinion slightly. "I had to work much harder in my math classes than some people did" or "I did not enjoy Algebra as much as Geometry" convey almost the same sentiment, without making the implied statement "Math was too hard so I quit trying. It's OK if you do the same."