How is Winston affected by the abuse of power?
The whole government in 1984 is one big abuse of power. The Party takes so much control over people's lives that it is not even funny. This is how Winston is affected -- he is oppressed by all the power that the government has over him.
Winston wants to have thoughts of his own but the government will not let him think openly. He wants to have true memories, but the government controls what the past is. He wants to have feelings for other people. Again, the government will not let him.
So everything Winston wants is denied to him because the Party is abusing its power.