You can very easily know for sure whether or not you are saved by simply reading the verses below and see if in your heart you truly believe these verses, and more importantly, if you are following them. If you are, then you can be 100% positive that indeed you are saved.
1) John 3:16
For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life.
2) 1 John 5:11
And this is the testimony: that God has given us eternal life, and this life is in His Son.
3) 1 John 5:12
He who has the Son has life; he who does not have the Son of God does not have life.
4) 1 John 5:13
These things I have written to you who believe in the name of the Son of God, that you may know that you have eternal life, and that you may continue to believe in the name of the Son of God.
5) John 5:24
Most assuredly I say to you, he who hears My word and believes in Him who sent Me has everlasting life, and shall not come into judgment, but has passed from death into life.
6) John 6:37
All that the Father gives Me will come to Me, and the one who comes to Me I will by no means cast out.
8) Hebrews 7:25
Therefore He is also able to save to the uttermost those who come to God through Him, since He always lives to make intercession for them.
Jesus said to him, "I am the way, the truth, and the life. No one comes to the Father except through Me.
10) Acts 4:12
Nor is there salvation in anyone else, for there is not another name under heaven that has been given among men by which we must be saved."
11) John 6:40
And this is the will of Him who sent Me, that everyone who sees the Son and believes in Him may have everlasting life; and I will raise him up at the last day."
12) John 11:25-26
Jesus said to her, "I am the resurrection and the life. He who believes in Me, though he may die, he shall live. And whoever lives and believes in Me shall never die."
There is but one door into heaven and Jesus Christ is that door, "I am the door and if any man enters through it and believes, he shall be saved." Jesus Christ is that door and he is the only way into heaven and the only way to obtain eternal life.
The apostle John told us that his purpose in writing his epistles was to show us how to achieve eternal life. 1 John 5:13, "I write these things to you who believe in the name of the Son of God, so that you may know that you have eternal life".
Maturing in your spiritual development
One of the very best indicators that you are maturing in your Christian walk and that you are drawing ever closer to Jesus Christ is if you have a constant and continuous hunger to know God, if you cherish the time spent alone with him, if you are always wanting just a little more knowledge about him, and if you seek opportunities to communicate with him.
Do you find yourself with an ever increasing desire to dwell ever deeper into the truth of God's Word? Do you find yourself meditating on the Scriptures hoping to glean a little more truth and knowledge from them.
Besides longing for God's fellowship and wisdom, a true mark of spiritual development is an awareness of your sinfulness and the importance of God's grace in your life. The goal here is your understanding of the incredible importance and the immensity of God's redeeming grace and the knowledge that you cannot out sin God's ability or his desire to forgive you.