The first step is to stop running away from the truth and recognizing that the relationship is indeed spiraling.
Relationships end, sometimes for the better, but there are always some factors leading up to an irresponsible breakup. Identify those problems and try to fix them.
If you really want to fix your relationship, you need to give it priority. Think about the time and effort you have been putting into it lately and rectify any shortcomings.
Sit down for a one-to-one with your partner. The longer you two delay this, the worse your relationship will get.
When you two decide to talk, you should be understanding and give your partner an equal opportunity to voice his/her concerns. It is important to put egos aside and discuss matters maturely like adults.
After both of you lay down your concerns and issues, you will need to assess the situation and seek solutions to the problems at hand.
If you decide to give the relation another shot, be open and forgiving. It is imperative that both of you let bygones be bygones and start afresh.
In order to give the relation a fair chance, make extra efforts and take time out to bond with each other again.
You can even take a vacation and go with your partner to an exotic location to reconnect and spend some quality time. However, don't be too controlling or manipulative.
Treat your partner. Bring gifts or take her/him out on dinner. Sometimes the fire in a relation needs to be rekindled.
Try rectifying your own mistakes for the long run. Don't be fixated on the past and try to move ahead with a positive frame of mind.