had it not been for .是虚拟语气省略if,助动词提前的强调倒装句.
I've discovered (that) i possess a large number of different talents and skills that [i never would have thought] were within me if it had not been for my being open to trying new opportunities.
I've discovered (that) 为主句 i possess a large number of different talents and skills 为 discovered 的宾语从句.
that i never would have thought were within me if it had not been for my being open to trying new opportunities.为修饰 a large number of different talents and skills 的定语从句.
if it had not been for my being open to trying new opportunities.为虚拟条件,如果不是我一直敞开尝试新的机会,i never would have thought were within me 为虚拟结果,其中 I never would have thought 为插入语,that were within me 为 定语从句中虚拟结果的主句.
而实际相反：由于我一直敞开尝试新的机会,我才会想到我有这些才华和技术.
（possess 少了1个s）
意思是：我发现我拥有很多不同的才华和技术,如果不是我一直敞开尝试新的机会,我永远不会想到我有这些才华和技术.