The concept of worthiness in a somewhat unique aspect of Mormonism. There are frequent worthiness interviews that one undergoes when fully participating in the church. Youth get interviewed quite frequently as they progress through the youth programs and Aaronic priesthood quorums. Adults get interviewed for temple recommends regularly as the recommends expire. There are also interviews for church callings. The individual conducting these interviews (particularly temple recommends and priesthood advancement) has a responsibility to determine the worthiness of the person being interviewed.
I have often heard people in the church express that we are never really ‘worthy’ of … anything. Never really worthy to go to the temple for example. There is a plain example of this in the first comment at a recent post over at 9 Moons here. What often seems to be missing is the acknowledgement of the gap between worthy and perfect.
To me, Mormonism has a more optimistic view of mankind. We reject the idea of total depravity, and believe that people can do many good things of their own free will and choice. When one combines the principle of repentance to our ability to do the things we should do, we can live in a condition of worthiness which allows us to participate in sacred things.
Being worthy does not mean that we have a completely and objectively perfect past. It means that we have repented of past sins and have a repentant attitude in the present. Worthiness is also not a claim of perfection. The Lord has set standards of worthiness through His chosen leaders, and anyone who meets this obtainable standard should feel confident in full participation in the sacred activities available to the saints.
Both the interviewer and the interviewee need to understand that there is a gap between worthy and perfect.