What would I change?
A wise colleague many years ago convinced me to start a 403B account. I did that, and I am very glad that I had some extra savings. My regret is that I didn't put the maximum into that account from the start. You hardly miss the money you put away prior to receiving your paycheck, and it really comes in handy later on. So my advice is that every teacher have a 403B account and that every teacher put the maximum into it. You won't regret that.
I continually invested in all kinds of professional learning throughout my career. That kept the job fresh and rewarding--I was able to employ new research and new ideas regularly which helped me to teach well and helped my students to learn well. My one regret here is that I didn't get all those extra credits under one big umbrella such as a doctorate or a specialist degree--that's what I'd recommend.
Over my tenure I created hundreds and maybe even thousands of lessons. I essentially wrote my own mini books to go with each unit and updated those books every year to match my students' needs and interests. I have many, many files that will soon be erased on the school computer. I wish I had created a good infrastructure for all that work on my own computer accounts--the kind of infrastructure that could essentially be easily turned into books to share, or perhaps, even publish. I hate to see most of that work go to waste as it represents substantial research and tried-and-true learning experiences that were successful. I suppose I could cull those hundreds of files, but I simply don't have the energy or motivation to do that now. Plus I suspect I'm headed in a new direction, so that information wouldn't be useful to me in my future roles. So my advice is to create a good infrastructure for all that research, writing, and content creation you do. That's valuable work that can keep on giving after your teaching career. I do have my blogs, however, which I'm happy to have, but unfortunately many of the links will no longer work.
Speak up and work for betterment
I did speak up and work for betterment. I wish I was a little more successful with this, but there were some successes with regard to my will to change school structures and elevate teacher leadership. I will be rooting from the sidelines for teachers to keep up that advocacy in order to make schools more equitable, positive, and successful centers for teaching and learning.
Keep the balance
Like many teachers, I worked around the clock. I gave my heart and soul to my work. I'm proud of that, but my advice is to keep a healthy balance. Do the required work to the best of your ability, but don't give up on your personal needs and interests--that's what makes life meaningful and that makes you a better teacher too. I'm happy that I always put family first, but now in hindsight, I advise not working around the clock, but instead, keeping a good professional commitment that matches the expectations for the job.
Seek help when you need it
Teachers are not superhuman--there will be times when you need help, don't be afraid to seek that help.
Know your contract
Teachers' unions are critical to the profession simply because teachers are very busy and don't have the time to advocate for what they need on their own. We need our unions and we need our contracts. Study your contract, join your local union, and stay active. When all union members are involved, teachers are treated better and enjoy better pay and better working conditions. This is essential to doing your best work by the students and their families.
There are many that will to infantize and belittle teachers. The way they speak about and to teachers is oppressive and negative. It is important for every educator to stand up and advocate for professional respect and support--the job of education is critical to the welfare of the country and world. Educators are important people who need to manage their careers in ways that support themselves and the students and families they serve.