What is core ? (I had to look it up) The dictionary says it is the central or inner most part of a thing, the most important part of anything. There are some things that wore us out, worries, getting old, fear of being misunderstood, being lost and sick, anxiety, alienation, accumulated little things,depressing news etc.
If you are a Christian and you feel one or more of the above, I'll suggest go back to our core (see definition above). What or who is our core ? Jesus is He. Jesus is the way, the truth, and the life, no one comes to the Father except through Him. John 14:6.
If you are not a Christian, or you are not sure you are one, study the claims of Jesus. Jesus could be the one you need.
By the way, this is Christmas season, this is supposed to be about Jesus Christ. Let us meditate on Him to the glory of God the Father. Put Him first, remind ourselves of Him.