Probably a part of my love of words that lead me to read dictionaries when I was 10 and encyclopedias for all the synonyms, pronunciations, origins and all that, i.e. acceptance doesn't mean to me--or to many others--what it does to you, and reverse it, it will be the same.
We all have different perceptions of anything from a thought string to words to uses for items and on and on.
So for me, acceptance is such a freeing word, and non-identification takes a load off me:
No self or condemnation of others, "and" when there is, look more deeply...
It's just "conditioning" for human beings to replace with recognition, acceptance, investigation and non-identification, or "not mistaking the murkiness (delusion) for Reality--learning not to do that; to replace delusion with what is really there/here.
I've never read or studied under any teacher who taught "only return to the breath," ever.
That would be relaxing, sure; it would, however always lead to other thoughts, i.e. "objects" because our human minds are made to be filled with objects:
So, which objects will there be; how will we respond to them?
Mindfulness is simple and as Bhante G. says, and every teacher I've ever heard, read or practiced with repeats, "It takes patience; courage; and determination...
It isn't a quick fix, so be prepared for the long haul."
Most give up, or never get deeper than relaxing.
If someone wants to do meditation for relaxing, that's OK.
It's not my goal, although it may be any number of other people's:
We share a common human malady, and how we deal with it differs from person to person, and within each of us, from time to time:
Nothing is permanent. It's all change, change, change...