Unfortunately (or fortunately) we do not ever know which day will be our last it could be today or it could be fifty years away there is no way for us to be certain how and when life's events will bring us to our last breath.
Many people will avoid thinking about this unpleasant thought and if you are not of an age where it feels more like a certainty it may be difficult to consider that you may not live for another few decades.

Therefore many people make no plans for what should happen if they pass away suddenly. This is of course perfectly reasonable of you are a fit and active thirty year old health addict. Unfortunately, even young and fit people die every day, and for many that means they leave behind loved ones who have to cope with the necessary arrangements in their already, darkest hour.
The solution, even for Mr. fit and healthy is to plan ahead, almost certainly your planning will be a few decades too early, but the possibility of putting your loved ones under added emotional stress while coping with loss should out-weigh the low risk. After all, we all have fire insurance but household fires are a comparative rarity, it's just that we plan for the worst and hope for the best.

The traditional funeral although still common is no longer the only option when planning your own arrangements, they have changed considerably over the past couple of decades with far more options available to anyone who is looking for different variations on the traditions.
One of the main options to consider is the "tone" of the service, in reality there are two options a more restrained or subdued commemorative ceremony or a slightly more relaxed or even "up-beat" service that is perhaps more a celebration of your life, rather than a direct mourning of your passing.
The there is how you wish your remains to be interned there is of course two main options burial or cremation, the numbers of cremations is growing each year, this may be due to the lower cost or the growing trend towards loved ones keeping the person that has passed with them or spreading their ashes at a well loved spot.

Next is the "pine box", the days of the wild west undertaker are over, so now there are many more options available in many different styles and materials including new environmentally friendly substances such as bamboo.
Whichever combination you choose funerals are not a cheap endeavor the average cost is now often over $10,000, there are many ways to keep these costs down if you plan ahead rather than leaving the decisions to already grieving loved ones who's judgment is probably already terribly impaired.
Pre-planning and pre-payment is a very effective way to remove additional financial and emotional burdens fro family and friend after you have passed, you can work out what you want in the cold light of day without the raw emotion that would be placed on others.

A little discomfort in planning your own funeral will be considerably less than that placed on others after your death.