It seems to me to be extremely difficult to be worthy of Christ's offer and to be truly obedient to Him. It seems to me that the people who think that Christ's grace is absolutely free and no worth is required of us are both right and wrong.
It is absolutely free and no worth is required of us in the same sense that a bucking bronco is absolutely available for free to anyone to ride and no worth is required to get on. To get on, yes, but to stay on?
Christ's offer is absolutely open and His love is available to everyone, yes. But that is just the beginning. It is a relationship that is on offer- one that is gratuitous, yes, and one that is sweet, yes, but also one with a true lover. A true lover loves you for who you really are, not for who you think you are. A true lover see you with absolute clarity, and wants to see you that way. A true lover does not humour your neurosis, your weakness, your self-destructive desires. A true lover is a bracing and yes, consuming fire, whose love will burn away everything not worthy of you.
We want to be faithful to Christ, and that is admirable. But the way that we sometimes choose to be assured of our own faithfulness is actually opposed to a real relationship with Christ. Some Jews tend to seek security in their fidelity to the details of the law, cloaking from themselves and others their failure to dance the true dance with the living God. Some Christians tend to take refuge in doctrinal propriety, believing that if we believe what we've been told the Bible says with perfect fidelity regardless of troublesome promptings of conscience or contradictory information from the world, then we are true to God. Then we have met the great self-sacrificial love of Christ towards us with requisite responsibility and gratitude.
Yet while we build idols with clear boundaries and well defined lines we are all the time obscuring from sight the real shape of Christs desire in us. Until we meet that desire something will always feel off- we will fail to acquire the real health that is offered to us in Jesus. Gratefully he will keep knocking at the door.