Learn your first language well. That means trying it for difficult tasks. Don’t obsess about technical details. Focus on techniques and principles.
Learn another programming language; choose any language that’s quite different from what you are best acquainted with. You can’t be a professional in the IT world knowing only one language. No one language is the best for everyone and for everything.
Don’t just do programming. Computing is always computing something. Become acquainted with something that requires your software development skills: Mediaeval history, car engine design, rocket science, medical blood analysis, image processing, computational geometry, biological modelling, whatever seems interesting.