Fill my cup, Lord;
I lift it up Lord;
Come and quench this thirsting of my soul.
Bread of Heaven, feed me till I want no more.
Fill my cup, fill it up and make me whole.

There is only so many miles we can walk, so much weight we can carry, and so much work we can do before we get tired.  After a few wipeouts, we learn our limits and most of us create boundaries to protect ourselves.  I totally agree with this, but find that some people turn these boundaries into walls and refuse to look outside of their own little worlds.  Still others say yes to everything and everybody, trying to make people happy.  I know that there is a balance and it takes years for most of us to learn what is right for us.

Whatever your hand finds to do, do it with your might
~Ecclesiastes 9:10

Therefore, my beloved brothers, be steadfast, immovable, always abounding in the work of the Lord, knowing that in the Lord your labor is not in vain.
~I Corinthians 15:58

That being said, we all have different jobs that God is calling us to do.  Some are physically demanding.  Some emotionally or spiritually draining.  We can’t ignore the work for fear of fatigue or pain.  We still have to dig in and get ‘er done.  Some people have told us that we work too much.  I don’t see it that way and have tried to explain my view on this time and time again.  When doing the work unto people, we will become weary very quickly because that type of service tends to come from our own strength when we try to please others.  When doing the work as a service unto God, it is a joy to be able to worship Him with the gifts and resources that He has given.  In ourselves, we are nothing.  All strength, leading, wisdom, direction comes from Him alone.

Whatever you do, work heartily, as for the Lord and not for men
~Colossians 3:23

Rendering service with a good will as to the Lord and not to man
~Ephesians 6:7

I recently read a devotion that summed this up very well and want to share it with you.  It pointed out that we should be emptied, but not exhausted.

I don’t know about you, but I understand things much better with a visual image.  When I think about the idea in this devotion, I picture a cup or container.  We are to be vessels inhabited by our Savior and Lord – filled with His spirit and love.    Surely, we want to pour that out into other people’s lives!  How could we keep Him all to ourselves?  At the end of the day, I want to know that I’ve emptied myself totally for His service.  If I keep going like that day after day without refilling with Him, I will become exhausted.  The essential part that we must remember is to refill our souls with His Word, prayer, song, fellowship with Him, worship, and whatever we need to do to recharge in Him.  That is the difference between being emptied and being exhausted.  Guard yourselves against exhaustion.  Find your strength in Him.  As long as we continue to connect to Him and ask for Him to fill our cup, we will have what we need to continue the work that He has given us to do.
Come to me, all who labor and are heavy laden, and I will give you rest.
~Matthew 11:28

My soul is weary with sorrow; strengthen me according to your word.
~Psalm 199:28

He gives strength to the weary and increases the power of the weak.  Even youths grow tired and weary, and young men stumble and fall;  but those who hope in the LORD will renew their strength. They will soar on wings like eagles; they will run and not grow weary, they will walk and not be faint.
~Isaiah 40:29-31