Matt. 28:20 Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, even unto the end of the world. Amen.
If this one is true, the skeptics ask, what about these?
Matt. 26:11//Mark 14:7 For ye have the poor always with you; but me ye have not always.
John 7:34 Ye shall seek me, and shall not find me: and where I am, thither ye cannot come.
It would help to read each of these in the context of their passages. First, John 7:34 is said to the temple police who are interested in capturing Jesus. It is a taunt based upon their supposed action in detaining and arresting the Son of the Almighty God, who can easily escape their grasp with power.
The first verse in Matthew is said in the context of the story of the woman anointing Jesus with perfume. It should therefore be patently obvious to all (except skeptics) that "with you" is said strictly in terms of physical presence that would allow acts like the anointing. (Indeed, the word Jesus uses here for "have" is echo, which more accurately means "hold" or "possess".)
On the other hand, the Matthew 28 verse is said by the resurrected Jesus just prior to Ascension in an eschatological context: re "the end of the age." This implies not physical presence but something of a more "supernatural" nature. Certainly the Gospel authors knew that Jesus was not going to be physically present with them at the time of the end of the age -- he had already left.