Do not worry! First of all, ask yourself why you want to be sponsored? Is the reason a natural progression? Or do you want recognition? Or do you just want bragging rights? Sponsors see through this.
Brands will sponsor an athlete because they see something in them that aligns with their product and ethos.
It might be that yourself and the brand are not an obvious fit.
You might not be at the level yet the brands expect from their athletes.
You might be an incredible athlete, but lack any presence on social media - which means the brand will need to work harder to promote you. YOU need to promote yourself.
You might be very similar to another well known athlete and so its been seen and done before.
Be nice. No brand wants to manage a difficult athlete. This also goes for if you are already sponsored - if the day comes when you want to jump ship and change sponsors, make sure you haven't burned your bridges with your existing sponsor.