Use the proper endpoint for removing your own reaction.

discord/http.py

@@ -386,6 +386,11 @@ class HTTPClient:
                   channel_id=channel_id, message_id=message_id, member_id=member_id, emoji=emoji)
         return self.request(r, header_bypass_delay=0.25)
 
+    def remove_own_reaction(self, message_id, channel_id, emoji):
+        r = Route('DELETE', '/channels/{channel_id}/messages/{message_id}/reactions/{emoji}/@me',
+                  channel_id=channel_id, message_id=message_id, emoji=emoji)
+        return self.request(r, header_bypass_delay=0.25)
+
     def get_reaction_users(self, message_id, channel_id, emoji, limit, after=None):
         r = Route('GET', '/channels/{channel_id}/messages/{message_id}/reactions/{emoji}',
                          channel_id=channel_id, message_id=message_id, emoji=emoji)

discord/message.py

@@ -701,7 +701,10 @@ class Message:
         else:
             raise InvalidArgument('emoji argument must be str, Emoji, or Reaction not {.__class__.__name__}.'.format(emoji))
 
-        yield from self._state.http.remove_reaction(self.id, self.channel.id, emoji, member.id)
+        if member.id == self._state.self_id:
+            yield from self._state.http.remove_own_reaction(self.id, self.channel.id, emoji)
+        else:
+            yield from self._state.http.remove_reaction(self.id, self.channel.id, emoji, member.id)
 
     @asyncio.coroutine
     def clear_reactions(self):