Sufficient, by definition, means "adequate" or "good enough." Usually. There is one other definition: "such that its existence leads to the occurrence of a given event or thing." In simpler terms, sufficient means that by one action, something else happens.
Have you ever heard that "His grace is sufficient?" Does that change the meaning a bit? That the fact that our perfect older Brother, even Jesus Christ, suffered and atoned for every sin and every sorrow that we will and have ever faced, is sufficient. It's not just good enough...its the ability to repent and return to live with our eternal Father in Heaven again, because we did live with Him before. What a precious, precious gift that we have been given! Utilize it, don't waste it or let it be for nothing. His grace is sufficient for you, no matter how much you tell yourself it's not.