The only way that I can be assured is by believing that this was carried out not only for all mankind but specifically for me. He did this because He loves me. He did it because He loves His masterpiece of creation. What is more important is that we are the pinnacle of that creation, being made in His image. He was not going to let that creation go to waste. He wanted a relationship with man and wanted man to have a relationship with Him. Jesus Christ, His son, came into the picture. Jesus Christ had to be born, live like man, be crucified and die and be risen from the dead. This glorified God and purified Jesus. God got something out of this. He got a Son. A Son who trusted Him completely.