-why do people cheat? because there is opportunity
-and still cry and beg and say it won't happen again, but still do it? because they are they don't want to lose what they have
-I am romantic I believe in love. Should cheating be forgiven more than once? NO, because it will become a habit for the other party
-does investing in a relationship for years is a waste of time? YES, if there is no improvement and harmony
-being cheated is the worst feeling. I AGREE, even cheated in grocery store makes you feel so bad, like when you are charged $19.99 for a sale price of $12.99, really worst when a person cheats on you.
-is a kiss consider as cheating? it depends, there are friendly kiss and romantic kiss

there are women who make attract or charm married or committed men for so many reasons, they want to prove that they can get what they want, they just want to ruin good relationship, they are selfish that they just want to satisfy their emotion without regard to others' feelings . . . and many more. there are men who just can't ignore advance move from women hence, they grab the opportunity, some men disregard consequences, and some men are really weak against temptations.

there are many answers to your questions, I hope you will be able to get them all.