Andrew F. Ehat describes a more limited sense of being sealed up to eternal life.
Andrew F. Ehat and Lyndon W. Cook, The Words of Joseph Smith: The Contemporary Accounts of the Nauvoo Discourses of the Prophet Joseph (Provo, UT: BYU Religious Studies Center, 1980), 26 n. 7
In a certain limited sense, a sense Joseph Smith used many times, the phrase "Holy Spirit of Promise" has reference to the concept of "making your calling and election sure" or "being sealed up unto eternal life" (D&C 88:3-5). Thus, when the Holy Spirit (who was the one appointed by the Father to give final sanctioning authority for all priesthood blessings) receives authorization from Jesus Christ to unmistakably "seal" the promise of eternal life on a worthy individual, he is placing the seals on the highest gospel ordinances in his office as Holy Spirit of Promise (D&C 132:7). The Prophet expressed this concept in his poetic rendition of D&C 76 (v. 53):
For these overcome, by their faith and their works,
Being tried in their life-time, as purified gold
And seal'd by the spirit of promise, to life
By men called of God, as was Aaron of old.
(Times and Seasons 4 [1 February 1843]: 84).