Without specifics it is hard to answer the questions. What is ‘fair’ depends on what you are talking about.
If you are taking part in decision making as a member of a committee you have to act in the interests of the OC. If you are voting at a general meeting of the OC, you can vote in your own interests.
I would suggest that if you have a conflict of interest as a committee member, you should 1) disclose that conflict and 2) abstain from voting on the committee on the particular matter, and 3) possibly absent yourself from committee discussion of the matter.
I also suggest you should make sure the committee minutes record that you absented yourself so that you can later show that you acted properly, should that turn out to be necessary.
I would not say you should always be protecting the OC bank balance at all costs. Sometimes the OC should spend. For example, the OC has an obligation to maintain the common property. If something is a significant safety risk, you should spend the money to fix it promptly and worry about recouping the cost later.
If a majority of owners don’t want to spend the money because they are cheapskates but a danger is clear and present and you are on the committee, fix the risk first and worry about the rest later.