Think about that for a second.
When you are preparing to take a heavy weight you take it seriously. You dig in your heels. You pay attention to your grip, your posture, your tightness, your stance, your coach's cues. You get a little excited and scared at the same time. Your 1-rep maximum (or a new 1-rep max, which by definition you've never lifted before) is a heavy weight.
But if you want to make the most of it, treat your warmup reps the same way.
Benching 5 x 45 as your first set? Make it five good, hard reps. Punch the weight up fast. Grab the bar with authority. Dig your shoulders into the bench and tighten up like a drumhead. Push each rep up with gusto and determination and speed, and pull each rep back down like it's the heaviest weight you've done.
Conversely, treat your heavy sets like the empty bar. Don't fear it, it's just a little bit heavier version of what you've been doing the whole workout. Probably less reps, even. Grip it and dominate the weight. Tell yourself it's nothing you haven't done for rep after rep all workout - and you have.
Then go get it done.
The way to do this is to make every rep a 1-rep max. Don't just rip out a few lackadaisical warmup sets, or a few early work sets with not quite perfect form, or not as fast or strong as you could have.
When every rep is your one-rep max, your one-rep max just another rep.