The salvation God provided at the Cross leaves no room for uncertainty. If you've received Jesus as your personal Savior, then the Father wants you to be 100-percent certain you're saved. There's a three-fold test you can apply to your understanding of salvation.
First, ask, "What does the Word of God say?" The Bible's teaching about salvation leaves no room for doubt. Acts 16:31 says it well: "Believe in the Lord Jesus, and you will be saved." That's it. It doesn't tell us to believe, plus something else. It just says, "believe."
Second, ask, "What is the witness of the Spirit?" Romans 8:16 says, "The Spirit Himself testifies that we are children of God." When we receive Jesus as Lord, the Father gives us His Holy Spirit. This ever-present Spirit inside enables us to relate to and communicate with God. Because of the Holy Spirit, we can continually testify that we're saved. Then, we'll be confident even if our feelings about salvation ebb and flow.
The third question you can ask to better understand salvation is, "What's the desire of my heart?" When the Spirit begins to reside within us, we'll experience powerful changes. We'll develop a desire for intimacy with the Lord and become sensitive to His will. This doesn't mean we'll never sin. But it does demonstrate our born-again spirit reaching for God.
You can know that you're saved. If you've made the commitment to trust Jesus Christ as your Lord and Savior, then rejoice today as a child of God.