Jesus is not a Guru or the Almighty God. He is the Son of God and so he tells himself.
About John 10:30, there is a few more things to compare with.
He also said in Matthew 19:4-6
"And he answered and said unto them, Have ye not read, that he which made them at the beginning made them man and female,
And said, For this cause shall a man leave father and mother, and shall cleave to his wife; and they twain shall be one flesh?
Wherefore they are no more twain, but one flesh. What therefore God has joined together, let no man put asunder."
We don't believe that they become two person in one! But they should be like one in forming a good unity and working for the same purpose.
And Jesus also said in John 17:20-22
"Neither pray I for these alone, but for them also which shall believe on me through theire word;
That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us; that the world may believe that thou has sent me.
And the glory which thou gavest me I have given them; that they may be one, even as we are one."
He wanted them to be united for the same kind of thingking and working for the same purpose as Jesus and his father in heaven. And he gave us the pattern to try to copy.