This can often be really challenging to do, but holding on too tightly to anger, sadness, the past or even control drains you.
In these final days of the year take the time to just relax. If someone is a dick, let them be and let it wash over you.
If you do something daft laugh at yourself (in one day I forgot my towel to get showered after the gym and had to dry myself with clean sweat bands and wrap my hair in my jogging bottoms then forgot to get off the train at my stop and had to get off at the next stop and get the next train back in the other direction).
If things are not going the way you want them to, there is probably a reason or lesson that you have to learn. Look for that lesson and grow from it…