Please Let Me Use Old Versions

So tonight I was like “I guess I should update wordpress” and i did and was like “ohh there is a new bar thing now. It tells me I need to update my theme”.. so i did. However, The updated version of my theme actually changed just the smallest thing on my webpage and now its like completely unacceptable for me to have this new version… pleeeeeease tell me its possible to activate the older versions of themes