Come unto Me, all ye that labour and are heavy laden, and I will give you rest. Matthew 11:28

There are to be found many who are actively engaged in seeking salvation; they believe that if they obey the precepts of the law they will be saved, and they are endeavoring to the utmost to do them; they have been told that the performance of certain rites and ceremonies will also save them, they are performing those with great care; the yoke is on their shoulders, and they are laboring diligently. Some are laboring in prayer, some are laboring in sacraments, others in self-denials and mortifications, but as a class they are awakened to feel the need of salvation, and they are intensely laboring to save themselves…Very speedily those who are active in self-righteously working for salvation fall into the passive state and become burdened; their labor of itself becomes a burden to them. Besides the burden of their self-righteous labor, there comes upon them the awful, tremendous, crushing burden of past sin, and a sense of the wrath of God which is due to that sin. A soul which has to bear the load of its own sin, and the load of divine wrath, is indeed heavily laden…The acute anguish of their souls will often be increased in proportion as their endeavors are increased; and while they hope at first that if they labor industriously they will gradually diminish the mass of their sin, it happens that their labor adds to their weariness beneath its pressure; they feel a weight of disappointment, because their labor has not brought them rest; and a burden of despair, because they fear that deliverance will never come. Now these are the persons whom the Saviour calls to Himself- those who are actively seeking salvation, those who are passively bearing the weight of sin and of divine wrath. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/0969.cfm