When you have to make decisions which you don’t have to justify to others, it is easier but could end up costlier. For example, why did you pick those 3 mutual funds to invest in? or why did you pick a particular term insurance? or why did you buy a particular phone/car/property to buy? and so on.
Of course no one has to justify all of your decisions to anyone but then you do have to justify to your older you. After you buy a phone or invest in a fund, you might get that nagging question - is this the best phone I could have got for that price or should I have researched more? or is this the best fund or should I have checked with someone else?
To avoid that regret at a later stage, you can share a write-up of why you chose what you chose to a friend, a peer or a mentor and ask them if it makes logical sense. They might have good questions and comments, that you might not have considered. This is not only helpful for personal decisions but also significantly improves the decisions at work.
A handy template is to write
Backgroud - Why do you think you need to buy that product or service. It could be diversifying your savings, want to learn a new language or instrument, need a faster phone etc.
Criteria for selection - List the criteria that you grade that product/service on and any weightage you want to give to a particular criterion
Options explored - Various products/services explored and how they rank on each of criteria.
Your recommendation - If there was no input from anyone else, you might have gone with that particular prodct/service.
Of course, you should not have think so deeply about every little thing. You can have some guiding principles that is a function of the cost or your time you need to invest in this. For example, if the investment cost is more than INR 5,000 or the time investment is going be more than an hour a day for a month or year (eg. learning a musical instrument).
So, write-up, share, get feedback and make the right decisions.