Starting again when it has been a long time
The way back is shorter than it looks from where you are standing. Whatever the gap has been, a year or ten years or most of your adult life, the Qur'an describes people who let prayer go and then, in the next line, sets them apart from ruin the moment they turn around. Sura Maryam names both: successors who abandoned prayer and followed their desires, and then Except those who repent, believe, and do righteous deeds.
Most people who stay away describe the same obstacle: the missed years have added up to a number too large to face. The Qur'an speaks to that arithmetic directly. The verse addressed to those who have wronged yourselves through excess tells them do not despair of God's mercy, and the sentence that follows is flat and unqualified — God forgives all sins.
It helps to recall what the prayer was given for. Musa is told to establish the prayer to remember me, which puts the practice on the side of remembering. Someone coming back after years away is doing what that instruction asks, and the remembering starts working from the first prayer.
In practice the return is usually one prayer, prayed badly, at the wrong time, in a room where nobody sees it. That counts. The instruction to establish the prayer at the two ends of the day and in the near hours of the night arrives with a promise about accumulation: Good deeds drive away bad ones. What to do about the years of missed prayers is a question for a scholar, and worth asking. Tonight's prayer does not wait on the answer.
The nearness that people expect to have to earn back is described as already in place: indeed, I am near. I answer the call of the one who calls when they call on me. The settling that follows is described as something the practice produces: hearts find peace in the remembrance of God. If prayer feels empty once you do return, that difficulty has its own page — when you feel nothing when you pray. If it is the distance itself that aches, see feeling distant from God.