“[“|But][W|w]hy do you call speak both of physical & mental ‘strain’?” – “Because they have a certain similarity, they have a common element.” Whatt is this common element can you point to it as you pointed in …? Can you say anything more about it than that it is the element of strain? If not, it was no explanation to say
“It is a certain tention.” That doesn't get us any further, for why do you talk of tension in these different cases.
“A certain feeling of tention

is part
accompanys

both experiences”. Are you not just translating what you said before, into other language

or are you actually referring to an experience like that of ˇfeeling your heart beat[.|,] Thus I could as you could say that this feeling accom is a constituent both of certain sensations of fear & of

joy
hopes

(2015–) Wittgenstein Source Bergen Nachlass Edition (WS-BNE). Edited by the Wittgenstein Archives at the University of Bergen under the direction of Alois Pichler. In: Wittgenstein Source, curated by Alois Pichler (2009–) and Joseph Wang-Kathrein (2020–). (N) Bergen: WAB.