What does « To lose / To neglect » mean in the Quran?

And thus we have made you a just community that you will be witnesses over the people and the Messenger will be a witness over you. And We did not make the qiblah which you used to face except that We might make evident who would follow the Messenger from who would turn back on his heels. And indeed, it is difficult except for those whom Allah has guided. And never would Allah have caused you to lose your faith. Indeed Allah is, to the people, Kind and Merciful.

They receive good tidings of favor from Allah and bounty and [of the fact] that Allah does not allow the reward of believers to be lost -

And their Lord responded to them, "Never will I allow to be lost the work of [any] worker among you, whether male or female; you are of one another. So those who emigrated or were evicted from their homes or were harmed in My cause or fought or were killed - I will surely remove from them their misdeeds, and I will surely admit them to gardens beneath which rivers flow as reward from Allah, and Allah has with Him the best reward."

But those who hold fast to the Book and establish prayer - indeed, We will not allow to be lost the reward of the reformers.

It was not [proper] for the people of Madinah and those surrounding them of the bedouins that they remain behind after [the departure of] the Messenger of Allah or that they prefer themselves over his self. That is because they are not afflicted by thirst or fatigue or hunger in the cause of Allah, nor do they tread on any ground that enrages the disbelievers, nor do they inflict upon an enemy any infliction but that is registered for them as a righteous deed. Indeed, Allah does not allow to be lost the reward of the doers of good.