We have already discussed this. None of that guarantees the individual heaven, at least from our point of view. A sealed person can lose their inheritance, as Paul writes to Galatians, Hebrews, and the Corinthians. God won't forsake His children, but WE can forsake Him, as Paul writes to Timothy and the above communities. He loved us while we were yet sinners, and continues to love us. While not a dogmatic teaching, many believe that God loves even those in hell. So God's Love doesn't necessarily mean a person is free from hell. But some people do not reciprocate His love in the least. Those who do not obey God's will cannot enter into His presence. I do not think there is a clearer statement from the entire bible...
The Scriptures seems to indicate that God hands over to His wrath those who refuse God and His will. Even Jews. Thus, Paul tells Christians to beware that they do not falter, as well. Persevering in Christ is a predominant theme in the NT. I do not think it is to be taken so lightly.
Regards
Reformers believe that perseverance is both commanded and absolutely necessary in order to get into Heaven. We do not take it lightly.