Regret is such a wasted emotion. Every experience you have ever had, has added value to your life. You may not have seen the value, but that is not proof that it had no value, it is merely an indication that your perspective at the time had blinded you to its value.
You will often be faced with choices and, being human, you will probably screw it up from time to time. I certainly do. Know this, this is the nature of life, and if you accept this and don’t beat yourself up about your mistakes, you will remain clear in your thinking and free from energy sucking, mind f**** (oops, sorry!!), mind destroying regrets.