But the true cause of regret boils down to one human flaw; that is, we can't see the future. If we knew the future with certainty, we could go about our lives without any regret, because we would truly know the 'right' decision to make at any time. However, since we don't, we are forever destined to stumble around, haphazardly guessing what will please us in the future, based off what has happened in the past.
That's where the problem arises- as humans, we are also notoriously bad at predicting how we will feel in the future. Got a bad tattoo? You obviously didn't imagine your future self feeling that way about it, in fact your 17-year-old self would probably be horrified that your 40-year-old self no longer wants to wear singlets that display your Tinkerbell tattoo with pride.
My point is, you can't be in the present while trying to live for the future. You can't go through life trying to figure out what your future self would want you to decide, because as a person, you're just no good at it.
This doesn't mean living hedonistically in the moment, but you've got to make decisions that are good for you right now, rather than getting captured by the future.
We are notoriously bad at predicting the future, so why would we want to live our lives based on what our future self may want? And if that means getting a tattoo, then so be it. Likewise with a juicer.
Tied in with that is not holding on to the past, ruminating on 'shoulda, woulda, coulda', but rather knowing that you did what seemed right in that moment. You can't change the past, but you can ask yourself what 'can I learn from the past, to inform my future, without beating myself up for past mistakes'.
Regret, unlike simply reflecting on the past and taking away lessons, serves no purpose. It is a great learning tool in that it will leave you mulling over what you could have done better, but after you have come up with your answer and learned from it, then it's time to move on.
So go forward every day with confidence. Don't get caught in analysis paralysis. Make the right decision for you at the time, and move forward knowing you did so. You can't fault yourself for being wrong about something if you stayed true to yourself, did your best and made the decision you thought was right. You would effectively be angry at yourself for being unable to see the future.
Do what is right, right now.
Forgive yourself the errors you do make. Take them on the chin, own up to them, and assess what you can gain from them. There is always something to be gained from any shortcomings or mistakes you make.
Do what you can to minimise the risk of anything that could make you have regret - take care of your body, of those who matter to you, appreciate what you have so you're not left saying "you don't know what you've got...".
And then just wing it. You'll be better off than trying to predict the future. Good luck.