If you contract COVID after the first dose of vaccination, you are more likely to have a less severe infection compared with if you were not vaccinated at all.
However, this is conditional. The vaccine takes about 2 weeks to stimulate the immune system to develop protective antibodies against the virus. If you were exposed to the virus prior to, during or immediately after vaccination, you can get an infection similar to the unvaccinated population. Secondly, if your immune system is compromised due to any reason (diabetic, cancer, organ failure, immunosuppressive medication) you may not form adequate protective antibodies to prevent an infection.
Therefore, the solution is to follow all preventive measures before, during and after the vaccination till the present wave and subsequent waves are over (do not travel outside unless necessary, maintain social distancing, wear a mask, wash hands, feet & face with soap and water whenever coming from outside). Get both doses of vaccine as recommended.