If I go against my parents and marry someone else, will my life be "bitter"

...you need to say, "I am the one saying yes or no. I am the one who will take responsibility for the success or failure of this marriage. I will not blame anyone else when problems come up. Why? Because I was the one who made the decision to go ahead with this marriage."

Do you know enough about that person to accept the match? If not, meet or at least exchange e-mails. If you have problems with something about him, talk to your parents if it is their suggestion. It is easier to get out of the marriage before the "I do"s than after.

If you marry someone else, then it sounds like a tradition you will be breaking. That is a lot to risk for a guy you are more emotionally connected with for now, and may not see unbiasedly.

Emotions change easier than Traditions.

Marriage is the biggest life changing experience (apart from dying). You want it to last many years.

Your family will be with you for all those years too. School friends loose contact with each other ... but family will always be willing to open the door. Break a tradition, and it may only be the backdoor.