"I hate to blow my own horn, but I gave a lot of people fits"

Bo Jackson's quote suggests that he was a formidable opponent in whatever activity he was involved in. He is being humble by stating he dislikes to "blow his own horn," which is an expression significance to boast about oneself. He is implying that he was so proficient at whatever he was doing that he gave a great deal of individuals fits, which is a phrase meaning to trigger somebody a great deal of trouble or difficulty. Bo Jackson was likely referring to his athletic prowess, as he was a professional athlete in both baseball and football. He was understood for his speed, dexterity, and strength, that made him a tough opponent to deal with. His quote is a modest way of saying that he was a formidable challenger and gave a lot of people trouble.