A vaccination makes you less likely to get sick, and much less likely to get seriously ill. The chance that you pass the disease on to someone else is also much smaller. So you also protect the vulnerable around you if you get vaccinated. If everyone is vaccinated, the less the virus can spread. A vaccination therefore protects not only yourself, but also the people around you.
The benefit of taking a vaccine is many times greater than the small risk of (serious) side effects. Being vaccinated doesn’t mean you can no longer get sick, rather, it is a layer of protection: if you do become infected, you become much less sick.
You could see vaccination as a precaution, just like putting on your seat belt. You can still get into a collision, but you’re much less likely to get seriously injured.