Here are a few sources for you.
http://www.freeinfosociety.com/article.php?id=184"At the Battle of Chickamauga, once again, Forrest saw a defeated and demoralized Union army before him (and he was once again correct), and advised an all-out attack. The next night, after the Union army had retreated into Chattanooga, he went to Bragg's headquarters, beside himself of the fact that the army had not moved against the enemy, and tried to impress on General Braxton Bragg the poor state of the enemy. Bragg (who always had some kind of excuse why not to follow up a near victory) asked Forrest how they could move against the enemy without supplies, and refused to order an attack. Forrest replied "General Bragg, we can get all of the supplies we need in Chattanooga." Bragg didn't answer, and Forrest stormed from the tent. Later, when Bragg ordered Forrest to turn over his troops, (the second time, he had also done it about a year before) and report to Gen Joseph Wheeler, a man that Bragg knew that Forrest hated, Forrest said to Bragg:
"You commenced your cowardly and contemptible persecution of me soon after the battle of Shiloh, and you have kept it up ever since. You did it because I reported to Richmond facts, while you reported damned lies. You robbed me of my command in Kentucky, and gave it to one of your personal favorites -- men that I armed and equipped from the enemies of our country. In a spirit of revenge and spite, because I would not fawn upon you as others did, you drove me into West Tennessee in the winter of 1862, with a second brigade I had organized, with improper arms and without sufficient ammunition, although I had made repeated applications for the same. You did it to ruin me and my career.
"When in spite of all this I returned with my command, well equipped by captures, you began your work of spite and persecution, and have kept it up. And now this second brigade, organized and equipped without thanks to you or the government, a brigade which has won a reputation for successful fighting second to none in the army, taking advantage of your position as the commanding general in order to further humiliate me, you have taken these brave men from me.
"I have stood your meanness as long as I intend to. You have played the part of a damned scoundrel, and are a coward, and if you were any part of a man I would slap your jaws and force you to resent it.
"You have threatened to arrest me for not obeying you orders promptly. I dare you to do it, and I say that if you ever again try to interfere with me or cross my path, it will be at the peril of your life."
(This quote was told after the war by Forrest's chief surgeon, Dr. J. B. Cowan. Cowan was the only person besides Bragg and Forrest that heard this exchange. Afterwards, Cowan exclaimed to Forrest, "Well, you're in for it now." Forrest replied, "He'll never open his mouth. Unless you or I mention it, this will never be known.")
http://en.wikipedia.org/wiki/Nathan_Bedford_Forrest"Forrest served with the main army at the Battle of Chickamauga (September 18 to September 20, 1863). He pursued the retreating Union army and took hundreds of prisoners.[26] Like several others under Bragg's command, he urged an immediate follow-up attack to recapture Chattanooga, which had fallen a few weeks before. Bragg failed to do so, upon which Forrest was quoted as saying, "What does he fight battles for?" [27] After Forrest made death threats against Bragg during a confrontation,[28] Bragg reassigned him to an independent command in Mississippi."
http://www.tennessee-scv.org/fg.htm"Nathan Bedford Forrest was noted for his hot temper"
"Forrest was just as angry at being successfully surprised by the Federals and young Gould bore the brunt of his anger."
Those are just a few, I can provide more.
Also, Bragg has the trait dispirited leader, this is a trait much worse than quickly angered. Bragg deserves every bit of that trait. I'm not debating that.