Don't waste time trying not to waste time.
If you really knew what time management is all about, you'd realize that time cannot actually be wasted because waste is determined by value, and value is determine on a highly subjective basis. In other words, value means different things to different people.
As Alexander explains in the video below, your own definition of value is what directs your decisions and subsequent behavior. What you find to be fun, exciting, and pleasant will be more attractive than what you find to be boring and/or painful. Therefore, your time management is a function of your own subjective determination.
Ultimately, you can't really go wrong. Time cannot be wasted, though, it can be spent without producing any sort of meaningful returns.
For example, if you unknowingly get sucked into social media for an hour, you've spent that time and can never get it back. Aside from the small hit of happiness hormones that flood the brain (i.e. dopamine), for most people there's relatively little value being exchanged for such an distracting activity.
If you're a social media influencer, on the other hand, it's probably your job to stay present in the social-sphere.
So "wasting time" comes down to your decision to engage in activities that you don't actually find valuable. This often happens when you're not being intentional with your time and energy, or when you allow other people to dictate your schedule (i.e. email).
Wasting time is more like a dimmer switch than an on/off switch. You'll notice that it scales up or down depending on your level of focus and the strength of your systems. The more you're "in the zone," the less you'll waste time. The better systems you have to keep you on track when you do lose focus, the more resilient you'll be when it comes to dropping back into the important stuff.
If you want to waste time, do so intelligently. That means anticipating your energy cycles and planning your work accordingly.
If you know that your energy slumps around 1:00 or 2:00 pm after lunch, then don't schedule anything important during that time. Instead, plan on doing low- or no-value tasks that need to be done, even if they don't offer anything in exchange. Things like running errands, cleaning, organizing—none of these require much skill or focus, yet they need to be done, so do them when focus is not required.
Or if you need a short break before starting an evening session of Deep Work, go do some brain melting on the couch and watch an episode or two of The Office.
In reality, you can't actually "waste time." But for argument's sake, let's assume that it's a thing. At the end of the day, everyone is going to waste time. The smart people (like you) are going to make sure that it's being wasted in a manner that serves you.