Write a diary. Or on pieces of paper,if you think "diary" is too feminine. Or a blog if you are tech savvy. Or a note if you spend all your time on Facebook. Write down your thoughts. Ideas. Incidents. Interactions.
You never know when the next big idea to change the world might strike you. You don't want to lose that.
Incidents teach. Recollecting the what and why and what could have been of incidents makes you wiser.
What you learnt could help many others. If all those authors hadn't written those textbooks,management books and novels,you wouldn't have been as intelligent as you are. Its only fair to contribute yourself. Don't be selfish. Share.
It is one of the strongest forms of expression. Of your personality,opinions,hopes and aspirations."Freedom of expression" is not a fundamental right without a reason.
We are engineers. Documentation is a virtue. You may forget what you may have done,and how. So write it down now,when you remember. If you still aren't convinced, think of a world without those setup guides, manuals and FAQ pages. Yes, that counts as writing too.
Writing is NOT showing off, as some people might say. If you can write, you have a gift and you are a fool if you let others stop you from using it.