“Not everyone who calls out to me, ‘Lord! Lord!’ will enter the Kingdom of Heaven. Only those... "who actually do the will of my Father" in heaven will enter. - Jesus (Matthew 7:21)

Only Joshua and Caleb entered the promised land because they "obeyed God completely" - They "wholeheartedly followed" the Lord. The Lord was furious with all the rest of His people... (Numbers 32:11,12)

We all know people who are, saved but immature, saved but unrepentant, saved but not disciples, saved but living in sin, saved but the Lord is not their first love, saved but not ready to meet the Lord if He should come for them by death or the Rapture.
 
Not all who are saved are Christ's bride.

And they said to him, “Grant us to sit, one at your right hand and one at your left, in your glory.” 38Jesus said to them, “You do not know what you are asking. Are you able to drink the cup that I drink, or to be baptized with the baptism with which I am baptized?” 39And they said to him, “We are able.” And Jesus said to them, “The cup that I drink you will drink, and with the baptism with which I am baptized, you will be baptized, 40but to sit at my right hand or at my left is not mine to grant, but it is for those for whom it has been prepared.”   (Mark 10:37-40)

(Not wise to assume everyone has the same position and reward)
“When you are invited by someone to a wedding feast, do not take the place of honor, for someone more distinguished than you may have been invited by him, 9and he who invited you both will come and say to you, ‘Give your place to this man,’ and then in disgrace you proceed to occupy the last place. 10“But when you are invited, go and recline at the last place, so that when the one who has invited you comes, he may say to you, ‘Friend, move up higher’; then you will have honor in the sight of all who are at the table with you. 11“For everyone who exalts himself will be humbled, and he who humbles himself will be exalted.” (Luke 14:8-11)
Heaven is a promise to those who are saved. To those who overcome - more is promised. To those who endure till the end heaven is guaranteed. Those who do not deny themselves and pick up their crosses to follow Jesus in this life are not "worthy" of Him. God is preparing a bride for Christ and she is "worthy" to wear the fine, white linen because she has made herself ready for Him. God (the Father) knows all of our hearts and it is He who chooses where we sit in relation to His Son.