Hey there!
i) firm decisions: "The New Year is a time for resolutions." A resolution is a firm decision to do something or to not do something.
ii) put together: "...most of us could compile formidable lists..." To compile something is to put together something by assembling information.
iii) overwhelming: "...most of us could compile formidable lists..." If something is formidable, then it is fearsome, overwhelming, or intimidating.
iv) unchanging: "...year in and year out with monotonous regularity." If something has regularity, then it does not change and it stays the same.
v) stumbling-block: "Aware of these pitfalls..." A pitfall is something that can get in the way, be a danger or a difficulty.
vi) restricted: "I limited myself to..." To limit is to restrict something in a way, including number, size, etc.
vii) with great zeal: "I applied myself assiduously to the task." Assiduously means to take great care and with perseverance.
viii) very tired: "...in an exhausted condition." If you are exhausted, then you are very tired and drained.
ix) give me away: "It was this that betrayed me." Being betrayed is to be exposed, or given away.
x) ward off: "...but I fended off the taunts and jibes..." Fending off something is to defend yourself from it, to ward it off.
Hope this helps!