There is a scripture in Romans the 8th chapter that states, "God's Spirit bears witness with our spirit that we are God's children". Those who partake of the new covenant emblems among JWs feel that is the verse that gives them the "sense" or feelin that they have been adopted as children of God.
Everyone else is warned not to partake of the emblems representing the blood and body of Christ, as they would be "drinking death to themselves" because they are not adopted as God's children.
This teaching denies the many verses in the Bible that teach Jesus gave his life a ransom for all who would believe in him. the problem that JW's have is that they believe that only those go to heaven that are in the new covenant, a position that I now consider a false teaching. Jesus made the covenant for a kingdom AFTER the Last Supper, (Lord's Evening Meal).
If Christ is your saviour, partake of the memorial emblems, whether or not you are one of the 144,000, which I also believe and have believed for decades that it is a symbolic number.
hope this helps