Why was the Confederate victory at Chancellorsville a costly one for General Lee?

The Confederate victory at Chancellorsville in May 1863 was costly for General Robert E. Lee due to significant losses, including the death of General Stonewall Jackson, one of his most trusted and skilled commanders. Jackson's injury during the battle not only diminished Lee's command structure but also had a lasting impact on the Confederate Army's effectiveness. Additionally, while Lee won the battle, the heavy casualties strained his resources and manpower, ultimately weakening the Confederate position in subsequent engagements.