It depends. If the balance between travelling, playing and spending time with the partner is easy to achieve, then being married can bring personal stability and happiness, which can only give you strength on court IMO.
It can have a negative effect, causing disinterest, losing focus (especially if there are problems) and mental lapses if in the honeymoon period.
Overall, I think marriage can be a positive. You just need to draw a line between tennis and your marriage. I would personally try and keep it as separate as possible.
Elena Dementieva AFR