The definition of success varies from person to person. Before you can judge whether or not someone has succeeded you must identify what they were trying to succeed at in the first place. This comes down to knowing your purpose. Why am I here? What am I here to do? What is my responsibility in this life? These are the measuring tools of success. Specifically no one can answer those questions for anyone else. Our Creator alone knows why He created us and gave us our unique personality and gifts. Therefore, the answer to these questions can only be found in seeking Him. This may sound a little cliche but it is true. That is why Paul said he counted all things as crap, (in the Greek this is the actual context of the word), so that he may "gain Christ and be found in Him"; not through religious righteousness based on doing the right thing and jumping through the right doctrinal hoops, but through the righteousness that comes by the grace of God through knowing Jesus. It boils down to relationship with Him. Incedentally there is only ONE reason God gives for not receiving them into heaven - "I never KNEW you." Therefore, for me, success is knowing Him, abiding in Him and obeying as He leads. Success is not found in perfection. I seem to blow it royally every now and then. It is found in submitting to His Spirit, repenting when I am convicted, and trusting that He will fulfill His purpose in me.
These are my whims, thoughts, musings, and reflections. Hopefully they will be an encouragement to you.