When Jesus walked the earth, there were many who sought after signs and wonders. After all, Jesus did perform many. He healed the sick, restored sight to the blind, and made the lame walk. He calmed the seas, turned water into wine, and turned the small lunch of a young boy into food for a multitude. He even raised the dead to life. But that was not what Jesus came for. Rather, He came to restore the relationship of mankind to God, which had been broken by sin. That could only come as a result of the belief that Jesus was who He said He was, the Son of God, the Messiah. But, people being people, it was the things they could see that they sought after, the miracles and the signs and wonders (John 4:48).
When Jesus sent the seventy-two disciples ahead of Him into the places that He was about to go, they returned full of joy that through His name they were able to cast out demons (Luke 10:17). They were looking at what they could see and what they were able to do, at their authority over the spirits of darkness. Jesus responded by affirming that He had given them such authority, but then directed them to what they should rejoice in instead, the fact that their names had been written in heaven (Luke 10:18-20). Their names were written in the Lamb's book of Life.
In our own lives, we should never let our joy come from miracles or signs and wonders. If we see these things, we should be thankful, of course. We should give God the glory due Him and praise Him for these things. But these things should not be the source of our joy. What should be the source of our joy? Our personal relationship with the living God we serve. Our peace with God, which we have through belief in Jesus and acceptance of His sacrifice for us, and the fact that through that peace with Him, we know that our place in heaven is secure - these are the things that should be the source of our joy.