Hebrews 4:7 God keeps renewing the promise and setting the date as today..."

The integrity of God's word cannot be over emphasized. God's promises does not ride on man's faithfulness but on His faithfulness and commitment. This is not to say that we can live anyhow, but you must understand that when we are unfaithful, He cannot deny Himself.

God's word will come to pass no matter the obstacles. His word abides forever in any situation. His word cannot return to Him void without accomplishing it's purpose. No matter how long it's been spoken, once there is a man to believe the same, there will be manifestation. 

When God speaks, it happens. God's word will not happen, it has already happened. His word is settle forever in any given situation. God is not agitative when it comes to His word, no panicking with Him. His word is forever settle concerning that sickness, homelessness, marriage, etc. 

We also as Isaac are children of promise. The covenant of blessings made with Abraham was already fulfilled in Christ Jesus for us to enjoy. Stop worrying, only receive His word and stand on it, it can never fail.

2 Corinthians 1:20 For all of God’s promises have been fulfilled in Christ with a resounding “Yes!” And through Christ, our “Amen” (which means “Yes”) ascends to God for his glory.

So in any given situation, get to know what has been said and done in Christ, if it was promised, then it has been fulfilled in Christ. Don't postponed it anymore, stand on His word, time is being reset for your sake, make His promises yours daily.