I've been learning Chinese for the last three years. I've been frustrated in my work during the same period of time. I've been learning Polish over the last year. I nearly went bankrupt in the last three years for unrelated reasons.

This provides me a good opportunity to discuss a related topic, the active voice.  Use of the active voice, instead of the passive voice, also avoids repetition.

I will provide only a quick comparison.

Passive verbs: is, are, was, were, have been, can be, and other forms of the verb "to be."

Active verbs: all other verbs.

Compare these two paragraphs and look at the verbs in italics. 

Passive voice: I am an ornithologist. That is, I am a person who studies birds. I am a botanist with a master's degree in botanist, but I am a zoologist with an undergraduate degree.  I am also a writer and editor and I am an ecologist. As a 61 year old man, I am approaching retirement.  I had been a botanist and ecologist for the U. S. Government for 17 years.  I hope I will be in China in April.  I may be there much longer.  I would be glad to hear if you have [not passive voice] any ideas for me about travel in China as a foreigner.  I can be obstinate.  I hope to be a good representative of America when I am in China.

Now, see how variety of active verbs makes this much more interesting to read.  After all, variety is the spice of life (but can make your wife angry if you use variety in the wrong way).

I consider myself as an ornithologist. That is, I enjoy studying birds. As a botanist I earned a master's degree in botanist, but I also wanted to work as a zoologist when I received my undergraduate degree in zoology.  I feel thrilled to also work as a writer and editor and I find work as an ecologist very interesting. As a 61 year old man, I see my retirement approaching .  I worked as a botanist and ecologist for the U. S. Government for 17 years.  I hope to travel to China in April.  I may stay there much longer.  I want to hear if you have any ideas for me about travel in China as a foreigner.  I often act obstinate.  I hope to represent America well when I visit in China.

Which is more interesting to read?  It took me 40 years to master the idea of writing with active verbs.  Using active verbs can also make you sound like a native speaker and a professional writer.