Figure out where it went all wrong
Think about why it happened, and what caused it to reach on such a level that you both had to consider separation. Go to the root of the problem and try to come out with possible satisfactory solutions.
Change old habits
Try to get rid of the old habits. These have been the main cause for all these problems in the first place. Therefore need to be replaced by new and more constructive ones. You'll realize that it was those small things that led to major arguments, which never got sorted out due to the constant repetition of such habits. In order to have a new start you need to reform yourself, and bring out the new you which is willing to work for saving the relationship.
Learn to accept criticism
The most important thing in a marriage is to accept when it's your fault, apologize and not do that particular thing again. This shows your commitment towards the relationship, as you are willing to compromise upon certain things by putting your marriage first. Learning to accept criticism doesn't only help you in relationships, but it also tend to make you a better person in general.
Talk it out
Misunderstanding often tend to be cause of arguments or fights which eventually lead to a separation. You need to make effort to clear those doubt away. It could be that your spouse is worried about something that didn't even happen, or is a huge misunderstanding altogether which needs to be settled by communication. Remember, communication is the key to a successful relationship.
Stay in touch with your spouse
Disconnecting yourself with your spouse will only worsen the situation. If you intend to save your marriage, you need to stay in touch with your spouse, and try to express your commitment by wanting to work things about you between you both. Your spouse may ignore you at times, or perhaps simply take time in getting back to you, but don't give up easily. It takes a lot of courage for making important decision such as separation, and it even takes more courage to reverse that decision.