labour of love

a labour of love (something that you do because you love doing it) - хобби, отдых для души; то, что делается от/для души, от чистого сердца, по зову сердца; ~отдушина

Example 1: ...Writing this dictionary of idioms is a labor of love; I do it because I enjoy working with language.

Example 2: They always want to pay me for the work I do at the hospital, but I will never accept their money. I do it because it is a labor of love.

Example 3: My Mom took care of her father for many years and kept her comfortable even after she became very sick; it was a real labor of love.

--------------
A "labor of love" is something that you do because of love or because you love to do it. "Labor" is work that we do and we don't always care for our work, but a labor of love is labor we do because we love dong it, or we do it for someone we love. Even the most difficult task seems easy to us when they are a "labor of love." (GoEnglish.com)

One volunteer is worth two pressed men

see also
[по зову сердца]
[для души]
[на голом энтузиазме]
[охота пуще неволи]