DON'T let your parents/friends/teachers/relatives think that it's "just a phase".
If living a compassionate lifestyle is important to you, let them see that! You'll show that you're serious and want to make a real change.
While many transitioning vegans/vegetarians may find it difficult to eliminate certain foods, you'll have it extra tough because your friends and family might be wanting you to slip up. Yes, I know that it sounds weird, but it's true. Some omnis take pleasure in showing that you're not 100% vegan, that you're not pure. The solution to this is either: a) try not to eat animals and their secretions in the first place, or b) take their silly criticisms in a calm way, telling them that you're doing your best and/or stil transistioning.
Also, don't let awkward situations comprimise your values. Sure, you might feel a bit bad for not eating some of Aunt Bertha's famous scalloped potatoes because of the cheese, but by acting in accordance with your values, you show how strongly you believe in abolishing animal exploitation.
I could write pages and pages on this subkect of being strong in your beliefs, but I've got to pack for HAWAII. I'm leaving at 1:00 this afternoon, and won't be back until the 1st or 2nd. Woohoo!