This topic is great for me, since I’m a senior too.
What everyone said is right, and I’ll repeat it.
As a student, you enjoy the success of the team by knowning that you’ve accomplished this and that in order to help the rest of the team win the award/the competition.
As a driver at my first year in FIRST, reaching as high as the Semi-Finals, I felt very satisfied with what me and my team have accomplished.
The feeling that you have as a student is uniqe and is only 3 times in a life time (for FRC, being from Sophomores to Seniors).
Now that I think of it retrospectivly, in 2008 I was the driver again, and once again our team had failed in the Semi-Finals, but this time I wasn’t happy at all. I actually cried.
And I might say that I had a reason to cry, since in my team the project is mendatory for 2 years and the third year as a Senior is voluntary and is counted more or less as young mentoring. And indeed I had cried since I understood that I wouldn’t have much to have to do on the robot for the next season, to say that it was THAT significant to the team’s victory.
The past two years in our team weren’t the most successful and only this year we had a great team of siriously dedicated students and mentors, and that is probably one of the reasons why we had a good robot and strategy for the Israeli regional and have won it, and I’m not sure I can say that this year’s success has a big part of it because of me, for several reasons.
My first goal in joining FIRST was to practice working in a business-like group, as a programmer, trying to build a prototype in a short time, in team work, and I believe that teamwork was very hard to be done in the past two years. I am not sure I have entierly been able to succeed in working in team work for the past three years for several reasons.
But I understood that I and any other Senior graduating HS should understand that life moves on. We had FIRST to learn our lessons for the future, for the exact things that we are about to come in to really soon.
That is why we should try to accomplish those goals we haven’t entirly been able to succeed in FIRST, or haven’t felt satisfied with the results. Find a good job with co-workers you find that you can work with, in team work and cooperation. Find the right way that works for you and your company to work to accomplish the companies goals, like in FIRST where you’d try to find the right goals that would fit your school, your sponsors, your parents and yourselves, the students. Work hard to have your company beat the rest of the competition in the market, just like you’d work hard to have your robot be better than other teams.
Continuing as a mentor probably has a slight diffrence from being a student, but not too much. I think that any senior should keep being active in FIRST as a mentor, since you keep learning more lessons from what the team does and how the team has done to accomplish what you’ve told them to do, to see if you were right.
Like I’ve said before, life moves on, and so should you. You’ve tried your best, but not always what you want actually happens. But you should at least feel good with yourself that you’ve tried your best to accomplish as much as possible while you were a student.
I know that I, as a programming team leader, a team CEO, a strategy team leader, a driver, a coach and an FLL mentor, have accomplished atleast the minmum of all I needed to have from FIRST.
Winning the regional, and having the chance to be in Atlanta, to compete and meeting the other famous teams is just a bonus. Though a rewarding one. I’m really for the idea that every FIRST team should have thier opportunity to experience the exictment going on in the crowd when the Einstien games begin.
If missing the field is the problem for you, don’t forget that mentors can be commanders/coaches. 
Yet I might be wrong.