This was sung recently, at church, and I found it encouraging. I know that I'm not the only person to post this hymn but wanted to put this up as it is so well worth reading.
The hymn is by Isaac Watts and differs from the original in that the third and fourth verses are reversed. The original also had another verse about Samson but , in my opinion, this is of lower quality than the rest.
Watts based this on 2 Corinthians 12 v 9-10:
He said unto me, My grace is sufficient for Thee: for my strength is made perfect in weakness. Most gladly therefore will I rather glory in my infirmities, that the power of Christ may rest on me. Therefore I take pleasure in infirmities, in reproaches, in necessities, in persecutions, in distresses for Christ's sake: for when I am weak, then am I strong.
Let me but hear my Saviour say,
"Strength shall be equal to thy day,"
Then I rejoice in deep distress,
Leaning on all-sufficient grace.
I glory in infirmity,
That Christ's own power may rest on me:
When I am weak, then am I strong,
Grace is my shield, and Christ my song.
But if the Lord be once withdrawn,
And we attempt the work alone,
When new temptations spring and rise,
We find how great our weakness is.
I can do all things, or can bear
All sufferings, if my Lord be there;
Sweet pleasures mingle with the pains,
While his left hand my head sustains.