Inheritance has nothing to do with how good you are, how bad you are or working toward gaining it. The word heir as defined in the New Testament Greek means one who receives his/her allotted possession(s) by right of sonship/daughtership.
In the Old Testament, God did not promise Israel's inheritance through a bunch of rules and regulations scholars know as The Law or The Law of Moses. God told Abraham that the "promise that he would be heir of the world" would come "through the righteousness that comes by faith." This instruction was given by the Holy Spirit to Paul to teach the believers in Rome.
UNTIL Christ Jesus, all believers in Yahweh could not appreciate and rightfully accept their Godly inheritance. The demand for kings to rule them and the bloody sacrificial system kept their inheritance at bay. The entire Law foreshadowed the coming of Christ to purchase the believer's redemption and inheritance. When Christ came and redeemed us through The Cross, Father God now saw Israel and all believers as full-fledged Sons and Daughters, not infants any longer. Earthly and heavenly inheritance were now available in abundance.
The question then becomes - What do believers inherit? A future, glorious location; a future, glorious, bodily existence; ruling and reigning with Christ plus the immediate presence of Jesus. However, there are blessings to inherit now because you are a Son or Daughter of King Jesus. Such characteristics as power, love and a sound mind or self-discipline are awaiting in abundance from The Lord. Sure, at the moment of salvation we have these inheritances and more in unlimited supply from God, however that does not mean believers are automatically perfected in them. Christians still have to own or take possession of their inheritance and grow in it with God's aid. Go then now, study what Christ Jesus has secured for you in His Word and by His Word and Start Living In Your Inheritance.