If someone is telling you if you take this step then your life will change forever. If your parents is saying that if you become doctor or engineer then your life will change. There is no such big or drastic change in your life. multiple small decisions become a big right decision. There is no big right decision. If you have decided that you will do something big then everything get messed up example as waking up early, making new friends etc.
If you approach your decision with shayad / may be then that is a better way than pakka decision.
This will prove out to be the best way for your decision if you can do so. if you can do this mentally then it will be good and if you do physically than great. make a dairy and write your wrong decision, specify time and date. This will turn out as a magic in your life. The decision which you thought are wrong then suddenly they become your coaching class or teacher. any decisions that you feel guilt of write it down then observe it without any emotions attached then it will do magic to your life.
Suppose you are fired from your job then how long you can survive so basically you should have enough savings for the bad days. make a list of what you dont want suppose you are married then you dont want another girl in your life, alcohol, cigarettes etc.
if you see all the decisions like alcohol, cigg, wrong decision reason behind all this is boredom. You should know to deal with your boredom. people do shopping, gambling when they are bored,smoke, watch movies, play video games when they are bored. These are the few things which provokes you to take wrong decisions.
you should always afraid of decisions that are based on other people. If you are taking a decision based on someone else intelligence then it will be going to be a big loss for you in future. listen everyone but if you dont feel right then dont do it.
even if you take a wrong decision then it will give you insight about your improvement but if decision taken by other people than you will blame others. massess cannot make right decisions only right mind can make it.