‘Laying up in store for themselves a good foundation against the time to come, that they may lay hold on eternal life.’ Do you mean to say, Paul, that what I do contributes towards my place in heaven? No, the apostle Paul isn't saying that.
So, if you want to avoid doubts and fears and shivers and trembling on your deathbed, or as the time approaches, be somebody who is given to the work of God in substance, in effort, in prayer. That will mean everything to you because it is what you cherish and love and desire and anticipate and work for. Bringing people into the kingdom by the power of the Spirit of God, you won't have the shivers and the fears and the worries that you could otherwise have had, but you will lay hold, you will go gladly into eternal life.