In Gal 2:8, Apostle Paul was saying that the same God who worked with Peter in his assignment also worked with Paul to accomplish his assignment. Friend every God-given assignment is important to God. God is ready, willing and able to work with you to accomplish your assignment.
However you must refuse to be intimidated by the assignment of others. Apostle Paul lived at a time when it was not popular to minister to non-Jews. He could have felt that his assignment was inferior to the assignepment of others. Rather he magnified his office.
Settle it in your mind today. Your assignment is important to God and to your generation. If this was not true, you would not have been created. So live your life like you have an important mission. Don't be distracted or discouraged by the views or comments of others. As you celebrate and prioritize your assignment, others will eventually celebrate your results.