In Acts 4, Peter and John were brought to the rulers and elders of the people (v. 8) to be questioned by them. But when Peter and John came to those people, who were Jews, they were astonished [by Peter and John]and they took note that these men had been with Jesus (Acts 4:13). In other words, the Jews could tell that Peter and John had spent time with Jesus simply by the way they lived.
Indeed, Jesus had so changed their lives that an "aroma" of God was coming from them. Having that "aroma" requires being like Christ, and the only way that we can become Christ-like is if we abide and dwell in God's presence--and doing that requires a conscious decision. You must decide to practice His presence!
Also, by being in God's presence, we will bear good spiritual fruit. In John 15:5, Jesus promises, "If a man remains in me and I in him, he will bear much fruit." In other words, by spending time with God you will develop valuable spiritual fruit. Then, the world will see your fruit and recognize that you have been with Jesus.
In addition, when you spend time in God's presence, you will experience an increase in your joy, contentment, peace, and satisfaction. Specifically, David told the Lord, in Your presence is fullness of joy (Psalm 16:11, AMP). Clearly, God will pour joy into your life when you spend time in His presence. Then, you can take that joy and show it to those around you.
There are great changes that can occur when you spend time with God. In God's presence is the only place where you can become more like Christ. Then, once God has changed you, the world will be astonished and see that you have been with Jesus.