First, "of my heart" simply means that something is associated with your emotions:
You are the love of my heart.
Also, when we use words like "heart" or "head" metaphorically, prepositions may not mean what you think they mean. Consider:
You really got in my head for a minute there.
That simply means, "You affected my thoughts," and (thankfully) has nothing to do with you shrinking and climbing into my skull.
As for "of my heart" vs. "in my heart", here's one way I might characterize the two:
- of my heart can be used with the definite article, to indicate preeminent personal feelings
- in my heart can be used with the indefinite article, to project a role
For example:
You are a diva in my heart. (means: in my heart, I regard you as a diva)
You are the diva of my heart. (means: in my heart, I regard you as the diva)
So, back to what you said:
"of my heart" sounds like you have several hearts, and one of them is your champion...
Instead:
the champion of my heart
means something more like:
there may be several people who could be my champion, but, in my heart, you are my true champion
Disclaimer: I wouldn't regard this as a hard-and-fast rule with zero exceptions. As was mentioned, prepositions are very tricky. Macmillan lists more than 20 possible usages of the word of, and when you combine those with metaphorical words such as head, heart or skin, some preposition-noun combinations will indeed be idiomatic, and need to be learned one-by-one (such as, "She really gets under my skin.")
There is no phrase "go a holiday" in standard English.
In British English one can go on holiday. In American English, one usually celebrates a holiday and goes on vacation.
Of course you can have a string go plus a holiday such as in
Wherever they go, a holiday follows.
This is grammatically correct and even a sentence someone might possibly say or write. But go a holiday is not a phrase in it.
Best Answer
The answer depends on exactly what you're trying to say.
We do not use in with holiday, except in the case of in the holidays, meaning "at some point during the period of time referred to as the holidays". If you talk about "in my holiday", you are not using idiomatic English - and definitely not British English. "In my holidays" is meaningful, but only to refer to a period of time like the summer holidays, the time pupils and students have without school in the summer. However, it's still an unusual turn of phrase. "In the summer holidays" is, however, idiomatic.
The distinction between holiday and holidays, in British English, is slightly more complex than singular versus plural. The idea of holiday can mean either when you go away from home for leisure reasons, in which case you would use an article:
Or some other determiner:
I'll get back to that choice between in and to later. You can also use on, rather than a determiner, in order to create a phrase that can be used to describe a state or as an adverbial phrase:
If you use holiday in this sense, and pluralise it to holidays, you are referring to multiple different trips.
Of course, a holiday need not be to another country.
The other meaning, referring to scheduled time off, is most familiar in reference to the six gaps in school each year - the summer holidays (usually but not always plural), the Easter holiday or holidays (can be either, in my experience), and the Christmas holiday or holidays (likewise), along with the three half-term holidays, each usually referred to as a holiday rather than each being holidays - each is a week long. You can talk about the school holidays and you might be referring to all six together, or to just one instance.
This meaning is also used in relation to adults for their time off work, especially where it is scheduled and the whole workplace shuts down. We have a system of legally guaranteed paid annual leave, but people will often refer to such leave as holiday, and having paid holidays.
In this sense of "time off", that may or may not include "going away", we can use the work in for the things that happened.
But we can also use during.
For the sense of a trip away, we wouldn't use in. We would tend to use on, for, and during, with slightly different meanings. If we did something for a holiday, that means it is the thing that represents the whole holiday.
That means that the entire trip is based around white-water rafting.
That means that you are consider Spain as the destination of your next leisure trip away.
On holiday is either used as an adjectival phrase to refer to the state of being on a leisure trip away, or to refer to things that happen while taking such a trip.
During a holiday is just a qualifier that says things happened in the course of such a trip, much like during for the other use of holiday.
This means that you want your next holiday to involve white-water rafting, but not necessarily to be entirely based around it.
So, to get back to your specific question, any of the following might be appropriate, but they have meanings that are different, subtly or not so subtly: