Often we switch between our tenses, past, present and future, and we don't notice when we do this. When we change the tenses of your verbs we create these shifts in time. It is best to avoid this.
Example:
Incorrect: I walked into the room, I am not alone.
Correct: I walked into the room, I was not alone.
The way that the sentence changes leaving the reader unsure of when the sentence takes place.
Make sure that you have chosen a tense, past or present. Once you have done this make sure you stick to it unless you are starting something new in a new paragraph.
Some shifts in time are obvious and necessary in your writing.
Example:
Playing computer can become addictive.Studies show, that there was many people who have played computer games last year.
In the second sentence it shows us why we need the past tense, it is based on past studies.
When writing, about ideas or events that have happened, in an essay make sure to use present tense.
Example from:Link
Hiking in bear country can be scary. When I was about 12-year-old, my father and I had an encounter with a bear in the woods. One day while hiking through a dense forest we heard some rustling in the thick bushes ahead of us. As we stopped and listened, the sound gets closer and closer.
When the sound stops, a huge brown bear rises out of the bushes, standing on its hind legs. My dad brought a gun in case of a bear encounter, so he pulled out and aimed it at the bear. The bear sees us and decides he wasn’t interested. Luckily, he didn’t attack and we didn’t have to shoot him.
“Hiking in bear country can be scary” (This sentence is correct. Even though the story is told in past tense, this general statement is a present, on-going fact.)
“As we stopped and listened, the sound gets closer and closer. When the sound stops, a huge brown bear rises out of the bushes, standing on its hind legs.” (Unnecessary to switch from past to present tense.: … standing on its hind hind legs” is okay and would work with either past or present)
“The bear sees us and decides he wasn’t interested.” (Unnecessarily starts in present tense.)
This example was just really amazing so I had to share it with you guys. Remember to make sure your shifts in time are not there or they are done right. Bad shifts leave your reader confused and they will have to go back to try figure out what you are writing.
Just on a little side note for self improvement. I will be doing pushups, situps and squats for the amount of $$$ I earn on this post and will give a short feedback every day at the end of each post. This will be split in equally between all 3. Any not done will carry onto the next day.
