How can I be sure my navel piercing won't reject?

If your body is going to reject it, sadly there is nothing you can do to stop, prevent, or reverse these effects. I just got mine done Saturday and I asked the guy about it and he said due to the type of medal in the intial rings it lowers the chances of rejection and if it does start to reject come in and they have rings made of different medals that are worth a SHOT but there is no guarentee's. Just stick to your cleaning twice a day. The only thing cleaning will help is infection which is very high in navel piercings but if cleaned properly with CLEAN hands and taken care of it should heal in about 2-3 months. Some say even as short as 6 weeks. Keep up the work and just try not to worry until something actually happens. NEVER put alcohol, or hydrogen peroxide on it. If infection does occur don't remove the jewlery as the hole can close in just MINUTES. Keep the ring in and get it looked at by your piercer,