The biggest reason why you should avoid office romance is that your life is no longer personal, it becomes an issue for the entire office and you lose your reputation. Your relationship is the hot topic for gossip; this makes the environment become tense for you and your lover.
A break up for co-workers who were once in a relationship is really bad. The feeling of not wanting to go to work to face your ex may creep up and this can lead to a bad performance at the office; which in turn, affects your career.
Seeing your lover every time can make your relationship boring after some time. This steals the spark and charm of your relationship.
Hope this helps.
A romance can go two ways: either it increases in intensity, in which case you will find it difficult to concentrate on your work and the presence of your desired one will keep you in a state of elevated emotion, which is bad for the quality of your work.
Or the romance goes downhill, you are disappointed and perhaps the desired one is now eyeing up someone else in the office. You may have shown your romantic feelings to the entire office and therefore invited gossip, Any romantic event or embarrassing happening will be known to all and make your days at work a total misery. Be sensible and keep work and romance apart.