3分钟内的话，考虑到语速应尽量放慢，以200字左右的为宜，鉴于你是初中水平，用语不太难，话题比较立志的。选了两篇供你参考。
Never give up hope
永远别放弃希望
Life doesn't always give us the joys we want.
生活并非总是如你所愿。
We don't always get our hopes and dreams, and we don't always get our own way.
希望有时会落空，梦想有时会破灭，我们不能一切随心所愿。
But don't give up hope, because you can make a difference, one situation and one person at a time.
但别放弃希望，因为事物并非一成不变；不同时间，不同场合，你会呈现不同的面貌。
Look for the beauty around you, in nature, in others, in yourself, and believe in the love of friends, family, and humankind.
处处留心身边的美吧---自然中的，别人身上的，你自己的——请相信，美来自朋友、家庭乃至全人类的浓浓爱意。
You can find love in a smile or a helping hand, in a thoughtful gesture or a kind word. It is all around, if you just look for it.
一个微笑，援助之手，关心的举止，友善的世界，无不传达着爱。爱无所不在，只要你肯寻找。
Give love, for in giving it you will find the power in life along with the joy, happiness, patience, and understanding.
奉献爱心吧，从中你会发现生活的力量，感受生活带来的幸福快乐，学会忍耐和理解。
Believe in the goodness of others and remember that anger and depression can be countered by love and hope.
相信人性本善。记住，爱心和希望能化解一切愤怒和沮丧。
Even when you feel as though there isn't a lot you can do to change unhappiness or problems, you can always do a little-and a little at a time eventually makes a big difference.
哪怕生活中挥之不去的不快和困难将你重重包围，让你力不从心，但你仍可以尽力而为。累积点滴努力，最终你将扭转乾坤。
PS：此篇稍短，我读了一下，大概两分钟
另一篇：
Life's Balance 寻找生活的平衡
Imagine life as a game in which you are juggling five balls in the air. You name them: work, family, health, friends, and spirit, and you're keeping all of them in the air. You will soon understand that work is a rubber ball. If you drop it, it will bounce back. But the other four balls--family, health, friends, and spirit are made of glass. If you drop one of these, they will be irrevocably scuffed, marked, nicked, damaged, or even shattered. They will never be the same. You must understand that and strive for balance in your life.
How? Don't undermine your worth by comparing yourself with others. It is because we are different that each of us is special. Don't set your goals by what other people deem important. Only you know what is best for you. Don't take for granted the things closest to your heart. Cling to them as you would your life, for without them, life is meaningless. Don't le t life slip through your fingers by living in the past or for the future. By living your life one day at a time you live ALL the days of your life. Don't give up when you still havesomething to give. Nothing is really over until the moment you stop trying. Don't be afraid to admit that you are less than perfect. It is this fragile thread that binds us together. Don't be afraid to encounter risks. It is by taking chances that we learn to be brave. Don't run thruogh life so fast that you forget not only where you've been, but also where you are going. Don't forget that a person's greatest emotional need is to feel appreciated. Don't use time or words carelessly. Neither can be retrieved. Life is not a race, but a journey to be savored each step of the way.
这一篇感觉文章比较有气势，最后一段，连续的don't 很适合带出感情，这一篇是三分钟