In the Protestant church there is joy and peace and assurance. If you accept Christ as Savior and Lord, you are taught you will spend eternity in heaven, and furthermore - you can be confident now, today, and every moment up to and including your death, that when you die Jesus will be there waiting for you, as He has promised.
Nobody has mentioned this, and maybe I shouldn’t either, but fools rush in…
The problem with the “salvation guarantee” is not primarily that it can lead people into sins they would otherwise have avoided. The main problem is if it isn’t true.
Say a person holds the “once saved, always saved” view, and feels sure that they have been saved. This causes him to ease up on the little sins. Lots of people would. I would (and in fact did) myself. The problem is that the little sins really
do lead to bigger sins. That is the Devil’s cleverness. And each sin is a larger or smaller turning away from God. You could find, in a number of years, that you had pretty much done a 180 and were steadily walking away from God. The little sins have gotten bigger and bigger, and now you’ve stopped praying and God isn’t a factor in your life at all.
The biggest problem with this scenario is that if you are wrong about “once saved, always saved” you are pretty much on the road to the Inferno at this point. You had no objective behavioral standards (in the form of rules, not suggestions) to tell you when you had started crossing the line, and no spur ro bring you back across it.
This is really one of the surprising joys of returning to the Church. It is actually very liberating not to have to waste your time making personal moral decisions about every little thing. It is easier to go to Mass every week then to fight with myself about whether it really matters if I go or not. It gives me more energy to try to be charitable toward the other drivers on the road, for example. And a couple of things I didn’t think were very sinful, but when I gave them up (because the Church said I had to) I realized the extent that they had been damaging my soul.
You are supposed to try hard not to sin,
What does it mean to “try hard not to sin?” How hard? How do you know when you are trying hard enough? I’m not trying to be funny–this was one of the issues I had. It’s too vague to be useful to me, anyway, although maybe it helps others. I kept veering between not feeling guilty because I hadn’t been to church in three weeks and feeling guilty for going to the grocery store on Sunday.
but it is expected that you will fall short, because that is the nature of man, to be a sinner, and each and every time Christ will forgive if He is Your Lord and His Father will forgive in His name.
This is also true in the Catholic Church. You only have to repent and ask (via Confession).
No amount nor number nor timing of sins could take from you your inheritance in Christ if He is your Lord.
How is Christ one’s Lord, if one is spending all one’s time sinning? Again, I’m not trying to be flippant, but there
has to be an amount of unrepented sin that really makes a difference in the end. “If ye love me, keep my commandments…”
In the Catholic Church, there is a list of mortal sins which I thought would include things that are easy to avoid - like murder, prostitution, thievery. But the list is long and deep and includes “thought sins” that are harder to control - I admit mean, petty, selfish, off-color and impatient thoughts pop into my head (seemingly unbidden) all the time. On a daily basis, for sure. And yet if I die without the opportunity for fresh Reconciliation - such as in a car crash, sudden heart attack, or other event without warning - even if my last Confession was just an hour before my death, nothing will save me from eternity in hell. Suddenly I’m afraid of laughing at even a slightly dirty joke forwarded in email and wondering whether being Catholic means having to email all my friends and ask them not to send anything not entirely pure lest I commit a mortal sin and not make it to Confession before my death. The Catholic Church may not demand actual perfection, being that it ‘allows’ venial sins, but I fear what it does require is more than I can achieve.
Let me make this perfectly clear, although I think it was mentioned before. ** It is not possible to commit a mortal sin by accident.** Never, under any circumstances can you do it. Do NOT worry about this. I actually had one priest give me a little lecture in confession about how my forgetting to go to Mass on a Holy Day of Obligation was not a mortal sin, because it wasn’t on purpose. (In fact I knew it, but I didn’t mind hearing it again.

)
As another poster pointed out, things that pop into your head unbidden are NOT sins. They are temptations. They only become sins if you willfully hold onto them instead of pushing them away. And I don’t see how laughing at a slightly dirty joke can be a mortal sin in any circumstances.
And about the question of getting hit by a car or something before you can make it to confession, maybe this will be a bit comforting:
Cathecism:
When it arises from a love by which God is loved above all else, contrition is called “perfect” (contrition of charity). Such contrition remits venial sins; it also obtains forgiveness of mortal sins if it includes the firm resolution to have recourse to sacramental confession as soon as possible.
God is not trying to send you to Hell. The Catholic Church is not trying to send you to Hell. Trust God. Also I can tell you from personal experience that knowing one will have to confess something helps you not to do it.
–Jen