(JOSHUA 3:5) - "AND JOSHUA SAID UNTO THE PEOPLE, SANCTIFY YOURSELVES: FOR TOMORROW THE LORD WILL DO WONDERS AMONG YOU."
The promise that God was going to do wonders among His people was conditional. The condition was that they sanctify themselves. Sanctification is the process of separating, or the setting apart of something or someone for service unto the Lord. God will not act on behalf of His people in the most powerful way if they are not inwardly clean and aligned with His will.
If we find ourselves fighting against the will and purpose of God for our lives there is the fact that we will not experience the wonders of God. A "wonder" is an astounding something that we can and will experience through our obedience to His will. God desires to move in astounding ways in our lives, but the condition for that to happen is the same as it was for the people that Joshua was talking to - being sanctified.
We can not live like, act like, talk like, think like, and do all the things that worldly and unsaved people do, and walk in the wonders of God. The wonders and the astounding and astonishing things are only promised to those who are living clean and Godly lives.