I remember in the first years of getting to know my chart, I absolutely did not identify with the stereotypes of Sagittarius -- especially the so-called happiness and positive outlook that is said to be the hallmark of the sign. And sure, you had astrological explanations for this: many planets in the 12th house, Pluto aspects to the Sun, Moon and Mercury, Saturn square ASC ruler, Saturn in 3rd, Moon parallel Saturn, Pluto and Saturn as the edge planets of my bundle chart and the list goes on.
However, with time I realised that in fact there were many things about me that were pure Sagittarian: I am more breezy in manner than I give myself credit for, opportunistic (in the neutral sense), I like to uplift others (which I do by being a problem solver and the guy you can brainstorm ideas with), and I actually have a basic belief in the future of positive outcomes. These realisations about myself came throughout my 20s and by now I am comfortable with my chart's ability to describe my personality and my life trajectory.
So learn more astrology and learn more about yourself overtime and you will realise that, so long as your birth data is correct, your card is an accurate description of the kind of person you actually are, and in ways that you may not realise or won't see manifesting until later in your journey.