I decided to write a series for my first published body of work and I think in hindsight it would have been less challenging to write a stand alone novel. If you start with a series, there is an inherent timeline you set that you need to keep or you will lose readership. That puts you up against the clock, there is good and bad that comes along with that.
Now that my first three books are published, I can take a breath and decide next steps. There are many things you learn simply by doing. I would invite all authors to finish their work, get it edited and then step into the arena. There is no replacement for that type of experience.
I love these questions about advice to your younger self, but honestly I feel like I received great advice/mentoring from various sources and I cherry picked what mattered to me at the time. There is no perfect advice, the perspective you have when you get older comes from experience and there really is no short cut to it. If I would give any advice it would be to own your choices and the results that come from them. That includes the bad. You will learn more from your mistakes than anything and as long as you don't repeat the same ones, you're on the right path. Keep going, finish your work and don't give up.
It's not a sprint, it's a marathon. Everyone knows that saying, but it truly applies to writing. Take your time, enjoy what you are doing and let your creative side dictate the pace. If you feel drained, take a break, go outside, take a walk etc. Do whatever you have to take care of yourself and fill that creative well