There is a concept of Yoshav Velo Avar Aveira, but that’s only when the situation comes up and you refrained because of the Mitzva. It could be that even if you can’t do it, but you have in mind that you will not do it now because of the Mitzva, it also has merit. I think I once heard of something like this.
The idea of Lefum Tzara Agra doesn’t negate S’char from a Mitzva that was easily come by – it only adds to it.