First of all, you need to maintain a physical distance when interacting with colleagues from the opposite gender. While friendly greetings have become common, you need to set certain physical boundaries for your own betterment.
If you are going to be holding a meeting with someone from the opposite sex, you should have a sit-down in a place where others can see you. It is advisable that you hold a conversation in the lunch room, boardroom, conference hall or a meeting room. This will ensure that the two of you only share a professional relationship.
While it is common for co-workers to have lunch together, you should try and avoid going to lunch with any particular colleague from the opposite gender. Not only will this prevent any feelings from developing, it will also keep your partner off your back.
However, if you have no option other than having lunch with a particular co-worker, you should ask other colleagues to come along so it becomes a group lunch rather than a lunch date of sorts.
Even if you are a very hard working employee, you should spend more time with your family. Try and go home on time after your shift an spend quality time with your spouse or partner. If you and your partner drift away, there are more chances of either of you cheating on the the other.
If you and your partner are having issues, it is always best that the two of you resolve them through discussion. Unresolved issues can lead to frustration and dissatisfaction, which consequently promotes infidelity.