Inclusive or exclusive?

Sometimes Jesus showed a very hard edge. He said to the potential follower who asked only to bid his family farewell, “Anyone who puts his hand to the plow and looks back is not fit for the kingdom of God.” (Luk 9:61-62) Then again He said, “Anyone who is thirsty may come to me! Anyone who believes in me may come and drink!” (Joh 7:37-38) So did Jesus have very high standards for those allowed into the kingdom or was it simple belief that was required? Is there a higher standard for a disciple than there is for a believer? Is there a difference between “inheriting the kingdom” and “having eternal life” (Joh 3:16). Does Jesus have different requirements for different people or different expectations during different situations? The hardest questions lead to the most satisfying answers. I’d love to hear your thoughts on this one.