When you feel bad, like you've disappointed God, because you've never converted somebody BUT you have tried and never stopped trying, don't feel so.
For Noah most certainly tried to warn his neighbours of the great flood God would send, but they did not heed him until it was too late. He must have felt really bad as well, but despite the fact he was scoffed at he didn't stop. Despite the fact that none but his family listened, he continued warning his neighbours and continued to build the Ark.
So if you never have converted somebody but kept trying nonetheless, what have you to feel bad about?
Seek first that you are secure in Christ yourself; dead to oneself and alive in Christ - and the peace, truth and love of Christ will be your portion, and may yet bring someone to meet Him and give their life to Christ who is Jesus, though you may not even know it until the Kingdom of God is established.