God will cause all that He promises to be fulfilled  -  Jeremiah 32:42

For thus saith the LORD; Like as I have brought all this great evil upon this people, so will I bring upon them all the good that I have promised them.

This promise was given to the children of Israel before they were taken captive by the Babylonians, but it can be applied to New Testament Christians as well, in a general way. We will suffer difficulty and face persecution but we can be assured that no matter what we experience, the good that God has for us will not be affected by it.