Acceptance (along with awareness) is one of the two skills that we're building when we practice mindfulness. It's an enormously deep topic/way of living that will keep unfolding for many years.
You can only accept what you're aware of, and we have been increasing our capacity for awareness every day. Now we will add to that a focused effort on building our acceptance muscle.
Acceptance is the antidote to our suffering, and is the polar opposite of reactivity, which is the cause of our suffering. Especially here in the early stages, acceptance must be expressed physically. It's too easy to think that you're accepting, when actually nothing's changed on an emotional or physical level.
Your fundamental gesture of acceptance is taking a deliberate breath – one that physically rearranges your body, expanding and softening it.
As you go about your day, notice instances of acceptance in yourself (maybe you ended up not throwing the stapler across the room today!) and out in the world (maybe someone let you merge into busy traffic). Keep taking those accepting breaths.