Instrutions are important in measuring how successful an individual would be, for example if given a task to clean two rooms in a flat, your success in that task would be determined by how well you carried out the instruction you were given. If you end up cleaning just a room, you would not be seen as very successful but if you clean the two rooms the way you were instructed to, then you can be called a successul individual.
The word of God is the instruction manual for believers in the life of righteousness, to measure your success as a believer, you judge yourself by the standards and instructions found in the word. For example the bible says “talk little, listen a lot, do not get angry easily, because you don’t do the right things according to God’s standard when you get angry” James 1:19-20. That’s not a suggestion but an instruction from the Spirit of God, so you measure how successful you are in this life of righteousness on how much you listen, speak and get angry and if you are found wanting, you simply change your course afterall the life of God in you has made you a master over every circumstance, a master over your emotions, feelings and words, so you practise talking less, listening a lot and never getting angry.
This is one reason the study of the word of God is so important, he gives you the guideline for your success as a believer. Follow the instructions you find in the word and watch yourself improve in passion and excellence.
Take fast hold of instruction; let her not go:
keep her; for she is thy life.