To forewarn means to inform someone of impending danger or possible problem.
In Ezekiel 2, God called Ezekiel to be a prophet and gave him a message for the rebellious and exiled Israelites. The Lord told him straight up that his was not an easy assignment because the people may not listen to what he had to say to them. He warned Ezekiel the task He was giving him would be a tough one because of the people's attitude and hardheadedness.
God, knowing that would frustrate the prophet and make him give up on his assignment told Ezekiel also in v.8 "But you, son of man, listen to what I say to you. Do not rebel like that rebellious people; ...” Ezekiel 2:8. God foreknew that Ezekiel would rebel and walk away when the people remained stubborn and unyielding to his words, therefore He forewarned him so as to ensure Ezekiel stayed the course in the face of severe challenges.
Before Jesus finished his assignment and departed the earth, He had a similar conversation with His disciples which applies to us who belong to Him as well. He listed some of the troubles they would encounter for His name's sake and for The Kingdom (John 16). He concluded with these comforting words; “I have told you these things, so that in me you may have peace. In this world you will have trouble. But take heart! I have overcome the world.” John 16:33. By telling them they would have trouble, suffer persecution, Jesus forewarned His disciples so they would be forearmed to handle the challenges that were sure to come.
We as followers of Christ also have and will have many troubles, challenges, difficulties, days of darkness, weakness, insults, calamities but there is hope for us. And knowing that Christ has already overcome the world, we are able to face and handle these boldly. We are able to endure because we know that victory is assured in the end.
So dear reader, fellow worker in the vineyard, fellow heir/heiress of the Kingdom, let your heart be at peace, rejoice always, even in sorrow (2 Corinthians 6:10) for the end of your story is already written, our Lord has already overcome and He has made us more than conquerors. Go forth today in confidence and push through any obstacles holding you back.