What some people consider encouragement, I consider pressure. I'm all for encouraging people to go after things that they want, but it's important to make sure that the other person really wants something before encouraging them to do it, because if you encourage someone to do something that they're unsure of, that's when the encouragement turns into pressure.
If a friend of mine wanted to audition for a play but was afraid they wouldn't be good enough, I would encourage them to go for it. I would say this because my friend may lack confidence, but they have indicated that they want to be in the play.
Now let's say this same friend is interested in auditioning for the play, but this time they're uncertain about the time commitment. This issue came up a lot in college, and here are some possible answers:
a. Rehearsals are normally x days a week for y hours.
b. You should email the director and ask about the rehearsal schedule.
c. Don't worry about it - I had the lead last year and took 4 AP courses and was in 10 other clubs.
d. Just go for it.
Both a and b are good responses. When a friend has a concern, it's best to provide objective information or suggest a way to obtain objective information if you don't know the answer yourself. I have heard a lot of college students say, "I do this and 10 other clubs," in response to people who aren't sure if they want the time commitment. While they may intend this response to be encouraging, it is actually a subtle form of pressure because it tells the person, "You should be okay with this because I'm okay with it." The fact that you're in the play and 10 other clubs has nothing to do with anyone else - you may like to be busy, but the play alone might be more than someone else wants to do. It's best to help your friend get all the facts so they can make that decision for themself.
The length of commitment and difficulty of backing out are also important to consider. If a friend is asking you about whether they should do something major, such as going away to college, it's even more important that you ask questions and not blindly encourage them to do something that they're not sure they want to do. You may feel like you don't want to discourage them, but if your friend is asking you about it, they must have some hesitations - otherwise, they wouldn't ask. When a friend asks me if they should do something or not, I ask my friend why they want to do it and why they don't want to it to try to figure out which choice they'll be happy with. Often, after questioning a friend, I find that they really do want to do what they were uncertain about and just need some reassurance. That's fine, but it's important to ask because asking creates an environment where you can do what's right for you.