Paul really wanted to see his fellow Jews know the Lord Jesus as their Messiah. Yet God sent him out to the Gentiles. Despite the many times that he approached the Jews to deliver his message, his effectiveness was really measured by the conversion of the non-Jews to Christ. Other Christians were called to the service of reaching out to the Jews; Paul's service was to the Gentiles.
What ministries has the Lord called you to? What ministries do you wish He had called you to? Don't waste all your time regretting the closed doors; simply say a prayer for those who are serving in those ways which you would like to (but can't) and move forward in the services God has invited you to participate in.